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SPECTRUM GLAZES PRODUCT GUIDE - 2003
ABOUT US
Spectrum Glazes is unique among ceramic glaze suppliers in that we focus exclusively on producing the highest quality, most colorful and diverse selection of fired finishes available anywhere. All of our energies are devoted to manufacturing glazes and other ceramic coatings. Our formulations have been developed over our 20 years in business with careful attention to detail, backed by our on-going commitment to thorough testing of materials as well as every batch of finished product. All of our products use ceramic frits and stains as their principal ingredients. This provides superior appearance and consistency of results over other products made primarily from raw materials, such as minerals and metal oxides. We also use a higher percentage of stains in our formulae which gives greater intensity, brightness, and depth of color to our glazes, underglazes, etc. We take great pride in our products and hope that you will get as much satisfaction from using them as we do from making them.
This Product Guide contains the following sections:
STONEWARE GLAZES - 1100 to 1190
GENERAL
We offer a selection of 75 cone 4/6 stoneware glazes. All of these glazes, except 1189 and 1190, are lead-free and dinnerware safe. Most of them also come with the A/P non-toxic rating from the Art & Creative Materials Institute (ACMI) which is clearly marked on the product label. Some of the reactive type glazes are rated C/L by the ACMI which means that they are considered toxic in the liquid (unfired) state due to the presence of heavy metals, such as copper, beyond the non-toxic legal limit. C/L rated glazes are not suitable for use by young children or pregnant women.
We have 3 types of stoneware glazes: clear glazes; plain colored glazes; and reactive glazes. These are described in more detail below. In general, clear glazes are used to cover designs created with underglazes. There is a choice of gloss, satin or crackle finishes. Our plain colored glazes are opaque and come in gloss and satin finishes. Some of our most popular stoneware glazes are the reactive colors which produce multi-tone and multi-colored effects by the combination of various metal oxides. Many other interesting effects can be created by layering these reactive glazes. In particular, layering a more fluid glaze, such as 1173, underneath or on top of one of the other reactive glazes often produces beautiful results.
All of our stoneware glazes are available wet in pints and gallons. They are also available dry in 10 lb. bags. The wet glazes are set up for brushing application. The dry glazes are set up for dipping application. For dry glaze mixing instructions see the sheet on "Dry Glaze Mixing Instructions" towards the end of this Product Guide. Please follow the instructions carefully especially with respect to the amount of water required.
CLEAR GLAZES
1100 Clear Gloss Glaze (cone 4/6) An excellent lead free, A/P non-toxic, dinnerware safe stoneware clear gloss glaze which is compatible with most commercially available underglazes. Like most clear glazes 1100 works best when applied thinly.
1120 Clear Satin Glaze (cone 4/6) Also lead free, A/P non-toxic and suitable for use over underglaze decoration. Satin clear glazes are not as translucent as clear gloss glazes and will tend to mute the appearance of underglaze decoration somewhat. It should be kept thin (i.e. 1 or 2 coats by brushing) to improve clarity.
1187 Clear Crackle Glaze (cone 4/6) A lead free, A/P non-toxic clear crackle glaze. After the piece has been removed from the kiln and allowed to cool the crackle pattern will form. A colored dye can be rubbed into the surface to emphasize the crackle pattern.
PLAIN COLORED GLAZES
Opaque Gloss Glazes 1101, 1102, 1103, 1106, 1107, 1108, 1109, 1110, 1118, 1131, 1132, 1134, 1135, 1136, 1137, 1138, 1151, 1164, 1165, 1166, 1167, 1168, 1169, 1184, 1185, 1186. A beautiful selection of lead free, A/P non-toxic, dinnerware safe stoneware glazes with particular emphasis on bright primary colors.
Opaque Satin Glazes 1121, 1122, 1123, 1124, 1125, 1126, 1127. Smooth satin finish on these stoneware glazes which are also lead free, A/P non-toxic and dinnerware safe.
Metallic Glazes 1188,1189,1190 Pewter, Gold Rain and Gold, respectively, are beautiful metallic finishes. Please note that they are not dinnerware safe or non-toxic and that 1189 and 1190 are our only cone 4/6 glazes that contain lead.
REACTIVE GLAZES
Reactive Glazes 1113, 1115, 1117, 1129, 1140, 1141, 1142, 1143, 1144, 1145, 1155, 1156, 1162, 1170, 1171, 1174, 1175, 1176, 1177, 1178, 1179, 1180, 1181, 1182, 1183. Are all lead free, non-toxic and dinnerware safe. They are formulated to produce reactions during the firing cycle which give very interesting and beautiful effects. The final appearance of the glaze is dependent on firing temperature, glaze thickness and the composition of the clay body being used. The same glaze can look quite different on different clay bodies. The samples shown on the color charts are 3 brush coats of glaze fired to cone 5 in an electric kiln on a white clay body. Different results should be expected in reduction.
Reactive Glazes 1111, 1148, 1152, 1153, 1154, 1157, 1158, 1159, 1161, 1172, 1173. Are all lead free but they exceed the vanadium and/or copper threshold limit in the liquid unfired state and therefore are not non-toxic. However, they are all food safe if fired to the proper firing temperature. They behave in the manner described above for Reactive Glazes. Also be aware that some of the colors, such as 1148, 1152, 1153, 1154, 1158, 1161, 1162, and particularly 1173 are more fluid and may run. Be more careful when using them on vertical surfaces. Use fewer coats towards the bottom of the piece.
HIGH TEMPERATURE CONE 9/10 GLAZES - 1200 to 1275
CLEAR GLAZES
1200 Clear Gloss Glaze (cone 9/10) Clear gloss glaze appropriate for use at cone 9/10. Lead free, dinnerware safe, and A/P non-toxic.
1201 Clear Satin Crackle Glaze (cone 9/10) A clear satin glaze which will crackle on most cone 9/10 clay bodies. Lead free, dinnerware safe and A/P non-toxic.
PLAIN COLORED GLAZES
Opaque Gloss Glazes 1206, 1207, 1208, 1209, 1210, 1215, 1226, 1229, 1240, 1241, 1242, 1243, 1244, 1245, 1254, 1270, 1271, 1272, 1273, 1274, 1275. Lead free, non-toxic and dinnerware safe range of beautiful opaque gloss glazes.
Opaque Satin Glazes 1203, 1225, 1231, 1237, 1248, 1251. Lead free, A/P non-toxic and food safe glazes that give a smooth satin finish at cone 9/10.
REACTIVE GLAZES
Reactive Glazes 1220, 1221, 1227, 1230, 1233, 1235, 1252, 1253. Lead free, A/P non-toxic, dinnerware safe glazes are similar in usage to the cone 4/6 reactive glazes but are for use at cone 9/10.
Reactive Glazes 1205,1222, 1228, 1234, 1256, 1257, 1258, 1259, 1260, 1261, 1262, 1263, 1264, 1265, 1266, 1267, 1269. Are all lead free and dinnerware safe but they exceed the vanadium threshold limit in the liquid unfired state and therefore are not non-toxic. However they are all food safe if fired to the proper firing temperature. They are also similar in usage to the cone 4/6 reactive glazes but are for use at cone 9/10.
MAJOLICA / ULTRAGLAZE COLORS - 301 to 366
Majolica/Ultraglazes Colors A highly versatile product which can be used as a majolica color on top of a white base glaze or as an underglaze color underneath a clear glaze or as a glaze on its own. For majolica technique first apply 2 or 3 coats (depends on how heavily you apply each coat) of our base white glaze (i.e. 799 Majolica White for cone 06/04 firings or 1118 White for cone 4/6 firings) all over the piece. After it has thoroughly dried you can decorate with the 300 series colors. One coat will give you the traditional majolica look in which some of the base white shows through the color. For opaque coverage 2 coats of color will be required. For use as an underglaze use the 300 series as you would our 500 series underglazes (i.e. 1 coat semi-transparent, 2 coats- semi-opaque, 3 coats- opaque) and then cover the entire piece with clear glaze (i.e. 700 Clear for cone 06/04 firings or 1100 Clear for cone 4/6 firings). The 300 series Majolica Colors can also be used as a glaze on its own, over the whole range from cone 06 to cone 6. It will fully vitrify at cone 06 but the surface will not be quite as shiny as our 700 series glazes. At cone 6 most of the colors will show little color change, except the pinks and purples which are not quite as temperature stable. All of the majolica/ultraglaze colors are lead-free, dinnerware safe and A/P non-toxic.
UNDERGLAZES - 501 to 566
Underglazes -A full palette of rich, vibrant colors that are opaque with 3 coats, semi-opaque with 2 coats and semi-transparent with 1 coat. They are compatible for use under most clear glazes. We suggest that you try them with one of our clear glazes (700 Clear Gloss cone 06/04, 250 Satin Clear cone 06/04, 1100 Clear Gloss cone 4/6, 1120 Clear Satin cone 4/6 or 1200 Clear Gloss cone 9/10). Unlike many other brands of underglaze we use a frit base rather than a slip (clay) base for our underglazes. The advantages to the user are that our underglazes can be applied on greenware or bisque and they can be used with or without a clear glaze covering. When used without a clear glaze cover they have a matte velvet like surface. However, when used without a clear glaze cover they are not considered dinnerware safe because the rough surface can be difficult to clean and can encourage bacteria growth. Our color chart shows the unglazed color in the upper left half of the tile and the color when covered by a clear gloss glaze in the lower right half of the tile. The color chart samples were fired at cone 05. Our underglazes generally have good temperature stability up to cone 6 and for many colors to cone 10. When fired hotter than cone 04 you may get small color variations from those shown on our charts, so please test them for your application. Our underglazes can be intermixed to create your own colors. However, we recommend not mixing 561, 562, 563 with any of the other colors. These colors are based on cadmium encapsulated stains that do not mix well with other ceramic stain colors. All our underglaze colors are lead-free, dinnerware safe and A/P non-toxic.
ONE-STOKES (CONCENTRATED UNDERGLAZES) - 600 to 636
600-636 One-Stroke (concentrated underglazes) Are intended as the name implies, to give opaque coverage with one brush stroke. They are ideal for painting on designs and can be used in the same manner as underglazes. They are very similar in use to the underglazes described above. However, they have approximately twice the concentration of color as the underglazes and are generally of a thicker consistency. All our one-stroke colors are lead-free, dinnerware safe and A/P non-toxic.
LOW TEMPERATURE GLOSS GLAZES - 700 to 816
CLEAR GLOSS GLAZE
700 An excellent lead free, dinnerware safe, A/P non-toxic clear glaze, which is compatible with most commercially available underglazes. It has good tolerance for a wide variety of low fire clay bodies and rarely crazes. We recommend applying it thinly (i.e. 1 to 2 coats by brushing) as it may cloud when applied too heavily.
OPAQUE GLOSS GLAZES
A wide range of lead free, dinnerware safe, A/P non-toxic colors, including excellent bright primary colors. These glazes require 3 coats by brushing for opaque coverage. In general, a more even appearance can be achieved by alternating the direction of brush strokes by 90 to the previous coat (i.e. first brush up and down the piece, next coat brush side to side). These glazes do not bleed together very much so they can usually be butted against each other without the colors running.
SEMI-TRANSPARENT GLOSS GLAZES
These lead free, dinnerware safe, A/P non-toxic glazes can be used to produce a multi-tone appearance since the color gets darker where they are thicker, such as in places where they flow into the details on pieces. Generally, it is best to apply them thinly (i.e. 2 coats by brushing). The exception in this group is 801, which is actually an opaque white glaze with black speckles.
DRAGON SKIN GLAZES 210 to 219
The eight colors in this series are designed to be used with our 250 Satin Clear to produce a textured and variegated surface which we call Dragon Skin. The technique requires that you first apply, on cone 03 bisque, one to three coats of the color. Let the color dry, then apply one to three coats of Satin Clear on top of the color. When the piece is fired to cone 06/05 a reaction takes place between these special colors and the Satin Clear glaze which produces the textured effect. Our samples show the results from using three coats of color and three coats of glaze. Other interesting results can be obtained by applying fewer coats of color and/or fewer coats of Satin Clear. Please do not use six coats (total) of glaze all the way to the bottom of the piece since such a heavy application of glaze will tend to move and could run off the bottom of the piece. Cut down the total number of coats to three towards the bottom of the piece. Also please note that color 218 Copper Green is significantly softer than the other colors and will tend to run more. This should be taken into account in the decoration of your piece. All of these colors are lead free. Colors 212,213,214,215 and 219 are non-toxic. Colors 216,217 and 218 are considered toxic in the liquid state due to the presence of copper oxide beyond the non-toxic limit and are therefore not suitable for use by small children or pregnant women. All of these colors are NOT considered dinnerware safe because the rough textured surfaces are hard to clean and tend to trap bacteria.
There are two additional products that can be used with our Dragon Skin glazes which are 210 Minimizer and 211 Maximizer. The 210 Minimizer is an additive that can be mixed with any of our Dragon Skin colors, 212 to 219, in order to decrease the textured effect. We recommend mixing one part 210 Minimizer with one part of any of the Dragon Skin colors. This mixture should then be used the same way the regular Dragon Skin colors are used (see above). The 211 Maximizer is an additive that also can be mixed with any of our Dragon Skin colors, 212 to 219, in order to increase the textured effect. We recommend mixing one part of 211 Maximizer with five parts of any of the Dragon Skin colors. This mixture should then be used the same way the regular Dragon Skin colors are used (see above). A very wide range of textured effects can be achieved by using different proportions of 210 Minimizer or 211 Maximizer with our Dragon Skin colors.
LOW TEMPERATURE SATIN GLAZES - 250 to 269
CLEAR SATIN GLAZE
250 This cone 06/04 clear glaze has a smooth satin finish and is ideal for covering underglaze designs. It should also be applied thinly as it may cloud if applied too heavily. It is lead-free, dinnerware safe, A/P non-toxic and also zinc free.
OPAQUE SATIN GLAZES
These cone 06/04 glazes provide solid coverage and a beautiful satin finish. They require 3 coats by brushing. Satin glazes tend to be stiffer and do not move much in firing, so an even application is important. They are sensitive to the firing temperature, in that the hotter they are fired the smoother and glossier the surface will become. They are all lead-free, dinnerware safe and A/P non-toxic.
LOW TEMPERATURE TEXTURE GLAZES - 271 to 278
These texture glazes are very matte and stiff and can be used effectively over the entire range from cone 06 to cone 6. They can be given an extra rough surface by applying the final coat with a sponge, which we have demonstrated on our charts. Although they are lead-free and A/P non-toxic, they are not dinnerware safe because the rough surface may tend to trap bacteria.
LOW TEMP. SPECIALTY PRODUCTS 120,122,138,144,145,170,817,818
SEMI-TRANSPARENT COPPER GREENS
817,818 Although they are lead-free these popular greens exceed the copper threshold limits in the liquid, unfired state and therefore are NOT non-toxic. However, they are dinnerware safe if fired to the proper firing temperature. 817 also produces interesting results in Raku firings.
CRACKLE GLAZES
138,170 Although they are lead-free and non-toxic, they are not dinnerware safe because of the possibility of bacteria growth in the cracks. After they have been fired to cone 06/04 and allowed to cool you can rub ink or dye into the cracks, in order to make the crackle pattern stand out the way it does in our color charts.
METALLIC GLAZES
144,145 Since they contain fritted LEAD, they are NOT non-toxic or dinnerware safe. 144 Pewter is quite a stable formulation and performs well at cone 06 to 04. 145 Bronze is a more sensitive glaze. It provides a beautiful golden bronze finish, if the thickness and firing temperature are correct. It needs to be applied heavily (i.e. 4 coats by brushing) and it needs to be fired hotter than normal (i.e. may require cone 03 or even cone 02).
CADMIUM LEAD GLAZES
120,122 They both contain fritted LEAD and CADMIUM and are NOT non-toxic or dinnerware safe. Unfortunately, this is still the only way to get these brilliant reds and oranges. These cadmium glazes are sensitive to glaze thickness and firing temperature. If the glaze is too thin the color may go silver in some areas. If the glaze is too thick or the temperature is too hot, black spots may develop. They should not be fired above cone 06. Also, a good supply of oxygen improves the firing characteristics of the two colors, so keeping peepholes open or ensuring that the kiln is not too densely loaded will help to get consistent results.
LOW STONE GLAZES - 900 to 924
900-924 Our exciting new line of low fire (cone 06/04) glazes that give the appearance of stoneware. The first nine colors have a glossy finish. 901 to 905 are semi-transparent two-tone glazes that produce a beautiful effect when used on pieces with some detail. 906 to 908) are glazes that break up and give one color in areas where they are thick and another color in areas where they are thinner. The remaining sixteen glazes (909-924), with the exception of 917 Terra Cotta, have a satiny finish and they will all break up to varying degrees. The exception, 917 Terra Cotta is a very matte glaze that does not react with any of the other Low Stone glazes. It is designed to give an appearance just like plain terra cotta bisque when applied on top of a white clay body. We have added 900 Clear to this line which can be used, for example, to line the inside of pots. Please do not use our 900 series glazes on the same piece with our 700 series glazes. Due to significantly different expansion rates this combination can cause pots to crack.
In addition to the chip samples in our color chart which show the result of applying 3 coats of each glaze on white bisque and firing to cone 05, please also look at the bell samples which show example of some of the wonderful effects that can be created by layering these glazes. These bells were done by putting 1 coat of one of the Low Stone glazes on the top half of the bell and then applying 2 coats of one of the other Low Stone glazes over the entire bell. We only had space to show a few of the numerous possible results that can be achieved this way.
All 24 of these glazes are lead-free and dinnerware safe when fired correctly. 16 of the colors are AP non-toxic, but 8 of the colors (901,902,903,913,914,915,923 and 924) have Health Labels for use in the unfired state. This is due to the presence of copper oxide and/or nickel oxide exceeding the prescribed limits.
CERAMIC STAINS - 2000 to 2090
Not to be confused with bisque stains which are not meant to be fired, these ceramic stains come in powder form and can be used to color glazes, underglazes, overglazes, engobes, slips and clay bodies. In general, they have greater temperature stability than many other commercially available stains. They are suitable for use from the lowest temperature ranges (cone 06) to the highest (cone 10) although colors may vary somewhat with increased firing temperature. For specific recommendations on each stain see Spectrums Technical Information Sheet. Our color charts show the results for the stains mixed in our 1050 underglaze base and fired to cone 06 and below the same chips fired to cone 6. The strength shown on these charts was achieved by mixing 100 grams of liquid underglaze base (3.5 oz.) with 50 grams of dry ceramic stain (1.75 oz.).
MISCELLANEOUS PRODUCTS - 1050 to 1074
UNDERGLAZE BASE
1050 Spectrums 1050 Underglaze Base is formulated as a base media for preparing your own underglaze colors similar to our 500 series underglazes. The 1050 Underglaze Base has some frit in it, which acts as a flux to help the stain be a compatible fit with either greenware or bisque. It also has various additives, which keep the frit and stain suspended and makes it brush on smoothly and easily. It is lead free, non-toxic and dinnerware safe when covered by a dinnerware safe clear glaze.
In order to achieve an underglaze of a strength similar to our 500 series Underglazes we recommend that you mix 1 part of dry powder ceramic stain to 2 parts wet underglaze base by weight. Therefore, for example, if you put half a pint (8 oz. or 228 gm.) of 1050 underglaze base in a container you should mix Ό lb. (114 gm.) of stain in this. This recommendation is only a general guideline as the strengths of different color stains vary and you should test colors, particularly the first time you mix them, to determine the correct strength for your application.
Spectrum Ceramic Stains (2000 series) are inter-mixable for the most part. However, we recommend that the cadmium encapsulated colors 2082, 2083, 2084, 2085 and 2090 can mixed among themselves but may not perform as expected when mixed with other colors. Also if you are trying to lighten a color by simply reducing the amount of stain used you may just produce a washed out look. We suggest instead that you try mixing in some of the 2000 White stain to lighten the color.
OVERGLAZE BASE
1060 The 1060 Overglaze Base is very similar to the 1050 except that it has additional frit to make the colors melt more easily and achieve a smooth glossy finish to the colors when they are applied on top of the majolica white glaze. Mixing instructions are the same as those shown above for the 1050 Underglaze Base. Lead free, non-toxic, dinnerware safe.
BRUSHING MEDIA
1070 Our Brushing Media is a simple gum solution that can be added to any glaze, underglaze, etc. to improve its brushing characteristics. The basic effect of adding Brushing Media to a product is to lengthen the drying time after the glaze is brushed on the piece. It also assists in glaze suspension. Brushing Media can be used if you are trying to convert a dipping or spraying glaze into a brushing glaze. The amount of Brushing Media that should be added depends heavily on the particular circumstances. A rough guideline is to add 5 to 10% of the volume of the product being adjusted, as a starting point. Keep in mind that the Brushing Media is largely water and that adding significant quantities of it will dilute the strength of the original product.
SUSPENDER
1071 Our Suspender is a solution of bentonite in water. It can be used to help suspend glazes that have become subject to settling out. The amount of Suspender that should be added depends heavily on the particular circumstances. A rough guideline is to add 5 to 10% of the volume of the product being adjusted, as a starting point. Keep in mind that Suspender has a strong tendency to gel and that the more you add the thicker or more viscous a glaze will become.
GLAZE THINNER
1072 Our Glaze Thinner is a solution of sodium hexametaphosphate in water. It is a very powerful thinning agent and should be added very sparingly. For example, 2 or 3 drops in a 4 oz. jar should have a significant effect. It is a useful product for thinning glazes, underglazes, etc. when you do not want to dilute the strength of the glaze by adding water.
STRIPABLE MASKING
1073 This is an organic rubber compound that can be applied to areas of a piece for the purposes of masking. It must be peeled off the piece before firing.
MENDING PASTE
1074 This is a mending paste that can be used to attach two pieces of bisque together. It does not develop its strength until after it is fired.
RAISED ACCENT COLORS - RAC 1 to RAC 16
RAC 1-16 Raised Accent Colors are slip-based colors (or engobes) which are available in 2 oz. applicator pens with a fine metal tip for decorating on greenware or bisque. They create embossed or raised designs on ceramic decorative work because the colors do not flatten out when they are fired. They are also available in 16 oz. squeeze bottles, which can be used to refill the pens or which can be used for slip trailing applications.
HOW TO USE THEM - Each 2 ounce squeeze bottle comes with a separate metal tip. After removing the screw cap from the bottle the metal tip can be screwed onto the plastic nipple. Before using the pen on your ceramic piece squeeze some out on a piece of paper to remove any air bubbles and to establish a consistent flow of color. When you are using the pen on a piece of greenware or bisque, hold the pen in contact with the piece. It makes it easier to control the writing than holding the tip above the piece and dropping the color onto the surface. Also the slight scratching of the surface improves the contact between the color and the piece. Do not hold the pen directly vertical when writing because this leaves no space for the liquid to flow out of the tip. Hold the pen at an angle to the surface so that there is an opening for the color to flow through. Because the color is quite thick you must write more slowly than with a pen so that there is time for the liquid to flow through the tip. You can create a large variety of line thicknesses by varying finger pressure and writing speed. The harder you press and the slower you write the thicker your lines will be.
HOW TO KEEP THE METAL TIP FROM PLUGGING - The liquid in an R.A.C. pen is similar to a colored slip and like slip it will harden in the pen tip unless you prevent it. We recommend taking a staple from your stapler and straightening out one end to use as reamer to push into the metal tip. It is helpful to leave the staple in the tip when the pen is not in use to prevent clogging. When you are finished using the pen for the day, the metal tip should be removed from the plastic nipple and the cap replaced on the bottle to prevent the pen from drying out. Also when you have an empty pen you should clean it out and fill it with water (see refilling instructions below). After you have finished using a metal tip you should screw it onto the pen filled with water and squeeze water through the tip to clean it out. Also, letting a used tip soak in water prevents hardening and plugging.
HOW TO REFILL AN R.A.C. PEN - In order to refill an R.A.C. pen you can remove the plastic plug from the top of the bottle. This can be done with a pen knife by inserting the knife edge in the seam between the plug and the bottle and gradually lifting the plug out. Then using the 16 ounce R.A.C. refill bottles you refill the empty bottle. Since the liquid is quite thick you may need to tap the bottle on a hard surface a few times as you refill it to get the liquid to settle to the bottom of the bottle.
GLAZE CRYSTALS CR01 to CR12
CR01 CR12 Our Glaze Crystals are all lead-free and dinnerware safe when fired to a minimum cone 06. These crystals are very versatile and can be used successfully from cone 06 to cone 6. They can be used with any glaze in this firing range to produce a great variety of different appearances. They can also be intermixed. Many beautiful combinations of two or more colored crystals on your choice of glaze background can be used. Please be aware that, due to varying expansion coefficients, some of these crystals may cause crazing on some glazes, particularly at stoneware temperatures. Please test for suitability in your application.
We recommend that the crystals be dropped or placed onto the final coat of glaze while the surface is still wet allowing the crystals to stick to the glaze. If the glaze dries out before all the crystals are applied try spraying a little water on the glaze surface to help the crystals stick to it. In this way you can position the crystals where you want them on the piece. However, these crystals will run a lot when fired up to cone 5 or 6 and should not be applied near the bottom of the piece for stoneware firings. This is not of concern at cone 06 or 05 as they will not move and spread nearly as much at lower temperatures. These crystals can also be mixed into a liquid glaze to be brushed on. However, one of the reasons that we decided not to prepare pre-mixed crystal glazes is that the crystals are large and heavy and tend to settle to the bottom of the container. Therefore, you will need to stir the glaze frequently if you choose to mix the crystals into a glaze.
RAKU GLAZES 850 to 867
850-867 Our Raku glazes were developed for firing in either electric or gas kilns. The firing process is described below. Three of our Raku glazes are not lead-free (857,858, and 867 contain lead and cadmium). Four of the Raku glazes are lead-free and non-toxic (850,851,854, and 856). All of the rest are lead-free, but are over the threshold limit for copper and are therefore not non-toxic in the liquid state. Our liquid glazes (available in 4 ounce, pints and gallons) are set up for brushing application. They can also be poured or dipped on pieces, although they should probably be thinned with a little water for this type of application. Our dry glazes (available in 10 pound bags) are set up for dipping application. Please follow our Dry Glaze Mixing Instructions for mixing procedures and for the amount of water required. 862 to 867 are not available dry.
Due to the many variables involved in Raku firing, particularly during the reduction phase, our chip charts and printed color charts should be used only as approximate guidelines. Your results may vary greatly.
RAKU FIRING Raku glazes can be fired anywhere from 1600 F up to cone 06 (1850 F) in either an electric or gas kiln. We recommend firing 850 to 859 to a peak of 1700 - 1750 F and 860 to 867 to a peak of 1600 - 1650 F. They should be allowed to cool in the kiln to 1600 F. Different combinations of peak temp and reduction starting temp will produce different results. While still red hot they should be transferred as quickly as possible into a reduction bin (typically a lidded metal garbage can or small metal container that has been lined with organic material, such as newspaper and/or sawdust, etc.). As soon as the pieces are in the bin the lid should be put on to keep oxygen from entering the container, in order to develop the reduction atmosphere. The pieces should be allowed to cool in the bin for at least 20 minutes. When the red hot pieces go into the bin the organic material ignites producing flames and smoke so this part of the firing, particularly the opening of the reduction bin, should be done outside.
FIRING TIPS
- Try to size the reduction bin to the size of the piece
- Establish a good seal to the reduction bin so that air is not entering and smoke is not leaving the bin.
- Position the organic material ( newspaper, sawdust, etc.) and the piece so that the flames can get all around the piece.
- Different organic materials may produce very different results, for example a glaze reduced in newspaper could be a beautiful blue color and the same glaze reduced in sawdust could have a metallic copper appearance.
- Pieces should be cleaned immediately with water and a hard bristle brush.
- After cleaning, warm the pieces in the kiln to evaporate any water from the piece. This helps to set the colors more permanently.
DRY GLAZE MIXING INSTRUCTIONS
SAFETY
The first thing to remember about any glaze in the dry powder form is that it is hazardous as a dust, so you must take care not to breath it. This is true regardless of whether the liquid form of the glaze is rated lead free and non-toxic or otherwise. Therefore when mixing dry glaze always work in a properly ventilated work area and wear a respirator and safety goggles.
GENERAL
On our price list you will find that all of our Hi-Fire cone 4/6 glazes are available dry in 10 lbs. bags, as well as wet in pints and gallons. Our standard wet glazes are all prepared for brushing application and our dry glaze are set up for dipping. Also, all of the Hi-Fire and Low-Fire glazes on our price list are available in dry form in 50 lbs. bags and can be prepared for brushing, dipping or spraying application.
PREPARATION
When preparing to mix either a 10 lbs. or 50 lbs. bag of dry glaze be aware that even through the powder is thoroughly mixed when it leaves the factory the components will tend to segregate as they are shaken about in shipping. The heavier components of the glaze will settle to the bottom of the bag. Therefore, when you are mixing dry glaze either use the entire bag or, if you only want to mix up part of the bag, make sure the dry glaze is thoroughly mixed. One way to mix up the dry glaze is to put it in a clean, dry 5 gallon plastic pail with a sealing lid. Rolling the pail on the floor for a few minutes should sufficiently mix the powder. Do not open the pail lid immediately after mixing; wait a few minutes for the dust to settle. Make sure you are wearing a mask.
MIXING
When mixing a glaze always use a clean vessel whose volume is at least 25% greater then the amount of glaze you expect to finish with. Put 90% of the required amount of water in the mixing vessel. Then immerse the mixer in the water and turn it on. Slowly feed the powder into the agitated water. The remaining 10% of water can be added if the glaze becomes too thick to mix properly. If the additional water is not needed hold it back to the end and add it gradually to adjust the viscosity and density. Mixing should be done with a powered mixer, which can be as simple as a drill with a paddle on the end of the shaft. Manual mixing is not recommended. After the glaze is thoroughly mixed it should be screened through an 80 mesh screen to remove any coarse particles.
HOW MUCH WATER DO YOU NEED?
The following recommendations are just guidelines to establish a starting point and the actual quantities required may vary. The following are some typical examples of the amount of water that is required to mix dipping glazes and the approximate amount of glaze that will be made.
Ratio of water to Dry Qty of water per Approx. Qty of
Prod. No. Description Glaze by Weight 10 lbs. of dry glaze Glaze made
700-D Clear Gloss Glaze(06/04) 0.78 7.8 lbs. = 6 Ό pints + 1 ½ Gallons
705-D Opaque Gloss Glaze (06/04) 0.63 6.3 lbs. = 5 pints + 1 Ό Gallons
1100-D Clear Gloss Glaze(4/6) 0.65 6.5 lbs. = 5 Ό pints - 1 ½ Gallons
1140-D Reactive Hi-Fire Glaze(4/6) 0.63 6.3 lbs. = 5 pints + 1 Ό Gallons
GLAZE TROUBLESHOOTING
SETTLING OUT
When a glaze "settles out" some or all of the heavier components of the glaze sink to the bottom of the container. If you try to use this glaze without thoroughly re-mixing it you will be applying a partial glaze with key ingredients missing. A glaze stays in suspension due to the presence of various types of suspenders, such as ball clay, bentonite and CMC gum. One of the common causes of settling out is the addition of too much water to the glaze, which dilutes the effect of the suspension agents allowing some of the heavier glaze ingredients to drop out of suspension. Another possibility is the growth of bacteria which will consume any organic materials, such as gum. This is of particular concern in the case of brushing glazes because gum is usually a large part of their suspension system. To prevent bacteria growth do not return used glaze, which has been poured out of the original container, back into that container. Also do not introduce potentially contaminated objects, such as brushes, into the original glaze container. Storing glaze in a hot or sunny environment may also encourage bacteria growth. Freezing can also destroy the action of gum, although in most cases frozen glazes can be gradually thawed and show no ill effects. If a glaze has settled out, but has not gone rock hard on the bottom of the container, it can be re-suspended by the careful addition of Spectrum's 1071 Suspender. After a glaze has settled out and been re-suspended it is generally a good idea to filter it through an 80-mesh screen to remove any coarse particles.
CRAZING
Glazes that have crazed show a fine pattern of cracks in the surface of the glaze, just the same as a crackle glaze although the latter is intended and the former is not. Sometimes the cracks are easier to detect by breathing on the piece and fogging the glaze surface. Crazing is the result of a mismatch between the coefficients of expansion of the glaze and the clay body. When the glaze has too high a coefficient of expansion relative to the clay body crazing will occur. The solution is to reduce this difference in expansions. This can be achieved by lowering the expansion of the glaze by adding a relatively low expansion material, such as silica, or by using a higher expansion clay body. You should be aware that delayed crazing can occur hours or even days after the piece has come out of the kiln if the expansion mismatch is close to the limits where crazing will occur.
SHIVERING
When a glaze shivers it cracks and pieces of the glaze peel right off the piece, often at the edges of the piece. This is the opposite condition to crazing where the expansion coefficient of the glaze is too low relative to the expansion coefficient of the clay body. One solution is to increase the expansion of the glaze by adding a high expansion material, such as a crackle glaze.
CRAWLING OR CREEPING
When a glaze crawls or creeps it will tend to mound up and expose an area of bare bisque. This often happens in corners where glaze has built up too heavily or has not flowed all the way into the corners. Glaze can crawl because the coat is too thick or because it has not adhered properly to the bisque surface. Improper adhesion can be from bridging, such as in corners, or from the presence of dust, grease, finger oils, or other dirt on the piece. Be careful to clean the piece thoroughly before glazing. Sometimes crawling is a defect of the glaze itself caused by the use of materials that have been too finely ground. Materials that have too fine particle size create an excess of surface tension, which tends to pull the glaze apart. Crawling may also be result of a heavy application of glaze, which is allowed to dry too fast, producing cracks in the unfired surface of the glaze. This will then lead to crawling when the glaze is fired. Putting on thinner coats of glaze and allowing the glaze to dry thoroughly between each coat can resolve this problem.
PINHOLES
One of the most common glaze defects is pinholes, tiny holes in the glaze surface that penetrate all the way through the glaze to the body. Pinholes are caused by gases that escape from the clay body during the firing cycle. The gas originates from tiny pieces of organic matter, such as charcoal, which is present in the clay. The best remedy in low fire ceramics is to ensure that the piece is bisque fired 2 cones hotter than it is glaze fired (i.e. when glaze firing to cone 05, bisque fire to cone 03). Other possible remedies include: a slower firing cycle; a 15 minute soak at the peak temperature; lowering the glaze firing temperature by 1 cone; using a glaze with more flux; and decreasing the amount of zinc or rutile in the glaze, if it is present.
BLISTERS
Glaze blisters look like little craters in the glaze surface and may have sharp edges. Possible causes of blistering include: insufficient drying of the piece between glazing and firing; too dense a clay body that traps air in the piece; gas forming impurities in the glaze or body; and a firing cycle that is too fast.
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