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I am in the process of writing an article related to the quick method of slaking plaster. Guaranteed to work, chemically sound with out the rigors of using a lb over a 30 to 40 day period without any chemical proof that the 1 lb of plaster has actually been completely slaked.!!!! This quick method of slaking is in my book, but I felt it needed some additional clarification. . Please feel free to use it, in your newsletter or for your personal information. Kindly give me credit if this goes into a society publication. .. Any additional questions, please post them here or contact me privately... . Here we go ! Go to any aquarium pet shop or pool store and buy an inexpensive pH testing kit. Usually 2 kinds. One set could have strips and another kind could have a chemical that's drops a drop of liquid in the water being tested... Either will work, but the liquid one is more accurate..A color chart is usually included. Get distilled water as your water source. Its pH is 7.0 Take any amount of unslaked plaster of Paris (Calcium sulphate.1/2 H2O or dental plaster (make certain its unslaked) lets say a tablespoon worth (you determine the amount you need to make) and put it into a small mixing bowl. Add about 4 oz of distilled (the amount of water is arbitrary) with a wooden spoon , stir vigorously so the unslaked plaster is agitated. You only need to do this for a few minutes. (the amount of plaster is small, so the stirring should be easy) The object: to prevent the plaster from setting. After, lets say 5 minutes, allow the plaster to settle on the bottom of the bowl . (plaster of Paris is insoluble in water so it will drop to the bottom... The water may be a bit murky at this point. Also, you may experience some heat which is natural in a chemical reaction..That would occur when contact is first made between the water and the plaster... Take a reading either by removing some of the water and adding the chemical in the pH kit or by adding a strip into the water to see what color it is.. Plaster of Paris is acidic and the color may vary but it will be orange to yellow range.. Then pour off the water, and add another 4 oz of fresh distilled water. Restir for about another 5 minutes, allow to settle and test the water again. You may see that the color has changed more toward the yellow to olive green. Again pour off the water, and add fresh distilled water again....Repeat the above process. Once a detection of blue appears on the color chart, the plaster is slaked.. No matter how much more water changes may occur, or stirring is provided, the plaster has now been slaked. The pH of the water becomes 7.0 or a greenish blue color and that indicates the water is neutral, and you just need to allow the plaster to dry out in a hanky or cloth and kept away from contamination. . Slaked plaster of Paris (Calcium sulphate 2 H20 ) the chemical changes once it increases its water molecules. For those interested, I can provide a photo of the color chart for easy viewing.. This method works, and you don't need to slave yourself for 30 to 40 days with a lb of plaster.. It can be easily made by the young and old .. It can also be purchased pure slaked if needed. I hope this information helps . Its simple, it makes sense, and its chemically accurate... Of course in the 14th and 15th century they did not have pH testing kits to determine when the plaster was slaked, but they did have other methods. That's another story for another time. JERRY TRESSER |