Coming Up Workshops Class Notes

EKEMENTS Mini Classes
Glazing Info

Commercial Brushing Glazes:

• Immerse piece fully into clean water.
• Use a soft natural bristle brush.
• Apply two coats for clear and up to 3 for colors.
• General thickness should be that of a dime.
• Let each coat dry to the touch in between each layer.
• If you do not know your glaze behavior, clear all bottoms by at least 1/2". Using wax resist will help you maintain an even border.
• If you see any glaze imperfections, such as little pin holes, now is the time fix them.
• Before loading into kiln, always sponge bottom to make sure it is glaze free.

Underglazing Info

Commercial Underglazes:

• Immerse piece fully into clean water
• Use a soft natural bristle brush.
• Use a soft pencil to draw your design.
• If applying to dry, unfired greenware, let each coat dry to the touch before putting on the next coat. One to two coats is sufficient for Spectrum underglazes.
• If applying to bisque, each coat will dry very quickly and be difficult to remove if you make an error.
• Greenware should then be bisque fired and then glaze fired. Bisque may be glazed after letting the piece completely dry for 24 hours.
• Most Spectrum underglazes will work at both lowfire and Cone 6.

Miscellaneous Info

Other Commercial Products:

• Spectrum crystals will work at cone 6 or lowfire.
  Crystals should be used only on the outside of functional ware.
• Engobes may be thinned or left thick to achieve a raised look.
• Spectrum Majolica Ultraglazes (300 series) may be used over or under a glaze or as a glaze. Most will successfully fire to cone 6.
• If you wish to do Scraffito (carving) through a slip, the slip should be applied when leatherhard.

Oxide & Stains:

• Oxides such as red iron and cobalts may be controlled by how much water is used. Both of these are very strong.
• Stains need a media to make them stick.

Surface Decoration Workshop Notes

1. Surface deocration may be visual or tactile.
A. Visual decoration includes:
a. various clays marbled together
b. varous glazes overlapped
c. terra sigilatta application
d. burnishing
e. colored clay inlay
f. underglaze painting

B. Tactile decoration includes:
a. additive (building surface up)
1. raised engobe
2. adding layers of clay to create depth
3. Sprigging
4. sponging
5. splattering
6. wax resist patterns
b. extractive (taking surface down)
1. carving, includes fluting
2. sgraffito
3. sanding
4. stamping
5. texture paddling
6. combing
7. pierced or cut outs

Terra Sigillata Instructions & History

Terra Sigillata was first used by early Roman and Greek potters. The very detailed, classic red and black pottery seen in museums and text books are beautiful examples of TS. This technique was lost for centuries and only rediscovered in the mid-1900's.

Terra Sigillata means "sealed earth". Terra Sigillata is a highly refined clay slip that is produced by levigation, meaning it is suspended in water to allow gravity to separate it into layers according to particle size. Only the very top portion containing the finest, sub -micron platelates are used. Because the slip is so fine, a very thin coat will produce a coating that will polish with the lightest touch of a plastic bag or soft cloth. This coating will be an integrated part of the pot, not like a glaze layer
Terra Sigillata can be approached in a very scientific way, or a more relaxed way. Both ways will work.

For a white TS that may be colored with stains or raw colorants use ball clay or gold art clay. Ball clays will give the whitest base. Both of these are very plastic by themselves and are air-floated. This means that you will get a greater amount of TS produced. These clays will not separate into a clearly defined layer, so just using the top 2/3 will work.

For a darker TS, use red art clay. This may also be colored, but only with darker stains or materials like red iron oxide.Note: This is a lowfire clay.

General, Easy Mix, Terra Sigillata Directions:
1. Add 1 part clay to 2 parts water. (1 cup clay, 2 cups water)
2. Mix with whisk, Jiffy Mixer, blender, ball mill or mortar & pestle. Be sure to break down any lumps.
3. Let mixture settle for 20-24 hours and mix again. Do not disturb it.
4. Add 7 grams of sodium silicate for every litre (1000 grams) and mix completely.
5. Leave undisturbed for 24 hours and siphon off the top layer, including any clear liquid.
Use several coats, letting it dry between each coat to give good coverage and then polish using a piece of light plastic bag over your finger, soft t-shirt, or small piece of flannel cloth.

More Precise, Ultra Refined, Terra Sigillata Directions:
1. Weigh out 1000 grams of the clay of your choice. The more plastic, the better.
2. Dissolve 0.25% (1/4 of 1%) or 2.5 grams ( .25%) of soda ash and 2.5 grams of wet sodium silicate in hot water. Next add this mixture to some cold water.
3. Add clay and more water into above mixture until the specific gravity of 1.15 for ball clay and 1.2 for red art clay is met. You must use a real glaze hydrometer for this. Mix completely.
4. Let settle undisturbed for 20 hours.
5. Siphon off the top mixture using a wine siphon (racking cane) available at wine making stores..
6. Dry out in bisqued bowl to store for later use or to thicken slightly for use now.

See Vince Pitelka's terra sigillata article #274 at digitalfire.com for further details about this method.

Glaze Layering Info

• Layering Commercial Products:
  
  You must always test the combinations before using on good pieces.
• Two separate glazes will combine and create a third. Layering will achieve totally different results than mixing wet glazes together and then applying.
• Allow each glaze layer to dry before applying the next.
• Combined glaze thickness should be that of a dime.
• Be very careful when layering that you clear the bottoms by at least 1/2". Combined chemistry can cause running.
• Some modifiers move considerably and should be kept on the inside or top third of the outside.

Mixing Dry Commercial Glazes:

• We recommend starting with 1/2 gallon of warm water to every 10 lbs of dry glaze.
• Mix the dry glaze slowly into the water while stirring.
• Run the glaze through a sieve to disperse the glaze and to break up any little clumps, add water if needed. Whatever is in the sieve needs to go back into the glaze bucket.
• Consistency should be like coffee cream or latex paint and give a glaze coat of around a dime's thickness.
• If you experience a noticeable settling you may need to add a suspender/binder like Bentonite, Spectrum 1071 Suspender or KPS Float-It. Even a little Epsom Salt solution will do just fine.
• Always wear a good respirator when working with any dry material and clean up with wet sponge or mop. Don't dry vac, unless using Nilfisk.

NOTE: Five (5) gallons of dipping glaze usually has 40 lbs. of dry weight.
Most 10 pound bags will yield between 1-1/4 and 1-1/2 gallon of wet glaze.
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Directions For Suspender Addition:

Epsom Salts:
Add 1 to 3 tablespoons of Epsom salts to just enough warm water to dissolve and add to wet glaze. Too much will cause the glaze to thin and settle.

Spectrum 1071 Suspender: Add 8 oz. to each 10 pounds that have been wetted.

Bentonite: Add 2-4% dry Bentonite to dry glaze before mixing.

KPS Float-It®: Add 8 to 16 oz. to every 10 pounds dry.

© 1997-2006

Kickwheel Pottery Supply, Inc. 1986 Tucker Industrial Rd., Tucker, GA 30084
770-986-9011 · 800-241-1895 www.kickwheel.com