Recipe for the Slip Recipe Or a Recipe That Has the Same Shrinkage Rate As Your Clay Body

DEFLOCCULATED SLIP FOR DECORATION by Matthew McGovern I like to use a deflocculated slip for the majority of my decoration. The beauty of using a slip that is deflocculated is that it shrinks less because of its low water content, allowing me to apply the slip quite heavily to leather-hard clay and not have it crack or flake off during the drying stages. Making a Deflocculated Slip Use 35% to 40% water to 100% of your dry material (example: if you use 1 100g of dry material you would use 35g of water). More water means more shrinkage. I try not to go over 35% water in my batches. Here’s a MONTHLY METHOD tip for translating the volume of water to its weight: 1ml H²0 = 1g Use your clay body recipe for the slip recipe or a recipe that has the same shrinkage rate as your clay body. Make sure you eliminate any plasticizing material from your dry clay recipe, i.e. bentonite, Veegum-T, etc. Depending on how runny you want your slip, use no more deflocculant than 0.25–0.3% of your dry weight. Mine usually works out to be 0.3% of the dry clay body weight. This measurement is approximate and is also based on the desired slip consistency. You can weigh out the deflocculant, but using a syringe that has milliliter measurements marked on it works fine. I have only used sodium silicate, but others, such as Darvan 7 and soda ash, can also be used. 2 I start by weighing out my dry materials (mixed thoroughly) and my water recipe according to my desired DEFLOCCULATED SLIP batch size. With the water Dry Clay Body . 100 .0 % weighed in a bucket, I Add: Water . 35–40 .0 % Deflocculant . 0 .2–0 .3 % begin to sift in the dry materials and start mixing. When the slip starts to get too thick to mix, I then start adding a few milliliters of deflocculant at a time to get it back to mixing consistency before sifting in more dry mix. A little deflocculant goes a long way. Toward the end, I keep a close eye 3 on how much dry material I have left to add and what the consistency of the slip is before I add more deflocculant. Too much deflocculant means a very runny and unworkable slip. Too little deflocculant means the slip will harden very quickly once applied. You can always add more, but you cannot take it back. If I find that I have added too much deflocculant, I weigh out more dry materials and start adding them to the slip. I try to avoid this at all costs because it messes up the ratio of materials to one another. Once the slip has been mixed, I screen it. A 20-mesh screen is fine, but I have found that two nylon paint screens placed inside one another work great and they eliminate tedious effort as they allow me to squeeze the slip through them. Applying the Slip When working with the slip, I gather a quantity of it in my hand and start 4 applying it to the surface of the pot as it is spinning on the wheel (1). Once the area of the piece is thoroughly covered, I clean off my hands, 1 Apply deflocculated slip to the surface of the pot as it grab my rib, then start trowelling the rib through the slip to get the line turns on the wheel. 2 Trowel a rib through the slip to get a pattern that I am after (2). I repeat the process for other sections of a specific line pattern or create ridges and planes using the slip. 3 Apply more slip to other sections of the pot. 4 Create pot, altering the pattern (3–4) There is a certain amount of cleaning up additional patterns and textures using your fingers. of the piece that is necessary, but this is done after the slip has hardened. 60 november 2012 www .ceramicsmonthly .org.

Load more