At 07:40 AM 2/16/02 -0600, you wrote: >I know I read once about pouring plaster into a box lid (like a copier paper >box) to create a surface for wedging clay--- I am a potter and this sounds like a reasonable way to make a wedging surface. I might line the paper box with thin plastic like you get from a dry cleaner (tape it around the top). PLASTER MIXING BASICS (for those who do not work much with plaster) 1. Put cool water into a plastic container or bucket (warm water speeds up the set time). 2. I start with about half as much water as the volume of the container I want to fill with plaster (if I need more I can add a second small second batch if I do it immediately. 3. Do NOT STIR. but fill all the water with dry plaster. If a mound of dry powder is above the water, spread it to the sides until it is all wet, but no liquid water remains on top (Plaster with too much water in the mix is very weak). 4. As soon as all the plaster is wet, stir with one hand or with a machine until smooth (it will get warm as it starts to set). Stir with the hand constantly submerged so as not to bring air bubbles into the plaster. 5. I wipe off my mixing hand on paper toweling and rinse in a bucket - never in the sink because plaster gets hard in drain pipes - even under water. 6. Pour it into the mold as soon as it is smooth. 7. Gently bounce, jiggle or vibrate the mold so bubbles come to the top while it is still liquid (the bottom surface may end up being the best for wedging). Sometimes I gently scrape the top to clean it up a bit. 8. Remove the block from the mold as soon as it is strong enough to handle. Handle with care. 9. Scrape the corners so they are rounded a bit and less apt to chip off (plaster chips in clay cause broken pots and pop outs after bisque firing). 10. Place in good drying location with blocks under it to allow air to dry it. This can take a week unless you have furnace vent or a fan to dry it faster. NEVER set plaster directly on a hot kiln to dry it. Too much heat reverts the chemical bond and it will turn to powder again. 11. NEVER put any of the wash-up water down the drain. Spread the water out on the grass. It will be help the lawn if distributed enough. After it settles for a few days the clear water could be poured down the drain and the thick stuff in the bottom could be placed in a trash can, but it may be too late to save the container if this system is used. I use disposable plastic buckets from food service or a sheet rock contractor. ADVANCED PLASTER THEORY 1. For a stronger mix try incorporating a bit of portland cement (use a rubber glove if mixing with hand). It will not be as porous, but it will be a lot stronger than plain plaster. Some potters wedge on a concrete floor. 2. I often cover wedging plaster with heavy canvas to keep from getting chips in the clay. It is best to have a wood frame so a staple gun or tacks can be used to attach the canvas. 3. A cheap 4 inch wide plastic putty knife makes a good tool to clean the wedging board. 4. Molding Plaster from a building supply house is okay for wedging boards and can be purchased in 100 pound bags. Be sure it is fresh by flexing the bag. Old bags are stiff and the plaster is no longer good. MIXING BY WEIGHT (copied from a CLAYART message) Courier NewFrom: Dan Taylor < Subject: Re: PLASTER MOLDS 1. Calculate the volume, in cubic inches, of the mold you wish to make(width x length x height) 2. 2 1/2% of the above answer equals the amount of water you require in pounds (100 cubic inches needs 2.5 pounds of water) 3. Determine what ratio of water: plaster you require. For working molds using potters plaster the water should = 70% of the weight of the plaster. (I have not tested this recipe) Marvin Bartel ---