$9.19
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Please note the "instructions" are in this description.
Not all standard quantities are pictured.
----> Go here to see other related listings for similar materials: <----
https://www.etsy.com/shop/NorthernWestStuff?ref=hdr_shop_menu&search_query=cement
https://www.etsy.com/shop/NorthernWestStuff?ref=hdr_shop_menu&search_query=plaster
Brief instructions (see below for more details at "More on how to use"):
Please note that this material has a recommended proportioning of 70 parts of water to 100 parts of plaster. It is a thick but pourable mix. As with all gypsum cements and plaster, it's much more accurate if you proportion it by weighing. It eliminates any guesstimating and results in the optimal end product.
Plaster shares the basic principles as gypsum cement mixing: Always add the plaster to the water, never the other way around.
Slowly sift the powder into the correct amount of water, let the water wick up the mound of powder and wet it, then start stirring. Use cold water at first, it will extend the working time. Use disposable plastic cups to mix it in (if you reuse a container it will accelerate the set so you won't have time to mix).
USG is the largest manufacturer of plasters and gypsum cements in the world and #1 Pottery Plaster is one of their products. They have technical sheets on mixing plaster with the proper percentage of water. There are also numerous written and video tutorials on mixing plaster. (if you're not familiar, the basics are: sift the plaster gradually into the correct amount of clean water, then mix. Those last two are crucial. You must use the correct water/plaster ratio or your end product won't be as strong and have the correct porosity/absorption when dry. A jiffy mixer on a drill is preferable).
This is the only "plaster" we carry. Similar to "Plaster of Paris" or just garden variety plaster, but superior. We have the stronger and harder "gypsum cements", most often put to use for castings. This, too, can be used for making castings; you'll find it to be better quality than the "Dap Plaster" sold by Home Depot. It's finer and more uniform. The practical difference between plaster and gypsum cement is in the water content and density (and the chemistry which makes gypsum cement stronger). Mixed plaster has more water, and when dry is softer and more porous than gypsum cements. These properties make plaster an invaluable tool for natural water bearing clay. And although similar to cheapo plaster, #1 pottery plaster has properties specifically designed for use with clay.
One uncommon non-ceramic use beside casting is carving. Why carving? If you've never carved, but want to give it a try, or even if you're somewhat seasoned, where do you get the chunk of "stuff" to carve? If you're a city dweller you may find a block of wood to be expensive. A block of limestone or marble even more so. Pottery plaster is relatively soft, smooth, and consistent. Cast a block or another shape into a mold made of soft clay and you have about the cheapest chunk you're likely to find if you don't have some land with a fallen tree and a chainsaw. A finished plaster surface can also be hardened and polished. And, I almost forgot, there's the making of sculpture by an additive process over a metal armature........
Here's a nice concise chart giving essential mixing info of plasters (from Laguna Clay):
http://www.lagunaclay.com/support/plaster-mixing.php
Here's a good data sheet from USG on #1 Pottery Plaster:
https://www.usg.com/content/dam/USG_Marketing_Communications/united_states/product_promotional_materials/finished_assets/usg-no1-pottery-plaster-data-en-IG1366.pdf
Here's a guide from USG on drying plaster. Drying Pottery Plaster is most important, since it affects porosity which is crucial if you're using it in concert with clay/ceramics:
https://www.usg.com/content/dam/USG_Marketing_Communications/united_states/product_promotional_materials/finished_assets/drying-plaster-casts-application-en-IG502.pdf
Most often #1 Pottery Plaster is used to make bats, wedging boards, and molds for slip casting. If you're already a potter or even a sculptor who works occasionally with real clay (water containing kaolin and etc worked to a dense malleable state), you'll know what the plaster/ceramics connection is about. If not, here's a brief explanation:
After mixing and drying, a plaster surface is quite porous. When moist or wet clay is in contact with dry plaster, water is drawn from the clay into the plaster. The surface of the clay against the plaster becomes drier, shrinks somewhat, and is very easily removed from the plaster surface. A "bat" is a disc of dry plaster that's attached to the wheelhead of a potter's wheel. When a wedged ball of clay is attached, wetted, centered, and hand thrown to form a shape such as a pot, the plaster allows the pot to be removed without damage.
A "wedging table" or board allows a chunk of inconsistent wet clay with voids to be worked by the process of wedging which removes excess water and air pockets until a proper consistency and plasticity are reached. The porous plaster absorbs water from the clay. Molds made of pottery plaster are the secret ingredient which makes the process of "slip casting" possible, which support a whole industry of ceramic dinnerware, sanitary ware, pottery, and decorative ware. "Slip" is a creamy liquid blend of clay, water, deflocculants, and other additives which is poured into (usually) multi-piece molds made of pottery plaster. Again, it's the plaster's porosity and ability to absorb water from clay which is key. After the slip is poured into the plaster molds, the water removed from the slip thickens it, turning it into clay which is strong enough to be self-supporting and removed intact from the plaster molds. Excess slip is poured out of the mold after the "skin" of clay against the mold becomes thick enough. Besides causing it to thicken, the plaster mold also causes it to shrink, pulling the outer clay surface away from the walls of the plaster mold, and greatly enhancing the ease with which the cast object is removed from the mold.
More on how to use ("instructions"):
Weighing is always the best way. If you have a digital lab scale that will measure grams (they are very inexpensive nowadays, check Amazon), weigh out the water and the gypsum cement powder. These types of gypsum cements want to be correctly proportioned. They are deflocculated like clay slips are (thus the thixotropy) to minimize the amount of water needed.
If you don't have a scale?
Forget about all of the above and do this instead (it's a bunch of guesstimating):
Please note this was written for gypsum cements. Plaster will be lower viscosity than gypsum cements.
Start with just a 4 or 6 oz container with a small amount of water (couple tablespoons or so) in it and start sifting plaster into it. Keep adding until you've got a mound of powder a half inch or so out of the water. Wait some seconds to see how high the water wicks up the mound for future reference (it should be just high enough to suck about all the water up into the mound), then start stirring. It should be paste-like but still stirable, and still be able to wet all the powder into a smooth consistency. If it stirs too easily you don't have enough powder in it. Sprinkle a little more in, since this is just a test. It should take some noticeable effort to stir. When you think you're there, pour it out of the cup onto some flat surface. Tap the cup as you pour. If it was a larger amount (like a quart), gravity would provide some force to keep it moving and pouring. It should form a thickish puddle on a flat surface and then stop flowing as its momentum slows. If it all flows off the surface you used too much water. If it won't pour out of the cup with tapping, just spoon it out onto your surface, then tap the surface. If it stays as an unmoving blob of cookie dough and doesn't spread out then you used too little water.
It would help if you repeat that a few times with just very small amounts until you get a feel for how far you can push the water/plaster proportion towards very viscous, but still being able to flow with tapping. The setting time is dependent on temperature, thickness of the casting, and the proportion of water/cement you ended up using. Poke at the puddle over the next hour or so to get a feel for how fast it sets. Using warm water speeds the set.
All of the above guess work is eliminated if you have a scale.
Here's a regurgitation of some of the information you'll find in the above links/URLs:
"#1 POTTERY PLASTER is highly uniform, noted for outstanding performance and long life. The standard of the industry - this is the best material available for sanitaryware and dinnerware casting. Used for making plaster bats, wedging boards, and working molds. The U.S. Gypsum Pottery Plaster is a relatively soft plaster which may be used for carving.
Preparing U.S. Gypsum Pottery Plaster: Use potable water at temperatures between 70° and 100° F (21° and 38° C). Since variations in slurry (the plaster and water mixture) temperature produce variations in setting time, it is important to keep both the plaster and water in a stable temperature environment prior to use. The higher the temperature of the water, the shorter the set time. Weigh both the pottery plaster and water for each mix. The water-to-plaster ratio is critical because it governs both the strength and the absorptive capacity of the mold.
Soaking Sift or strew the USG pottery plaster into water slowly and evenly. Do not drop handfuls of plaster directly into the water. Allow soaking for 1-2 minutes. The plaster should be fully dispersed in the water prior to mixing. Small batches require less soaking than large batches."-
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May 5, 2023
Leslie Hsieh
Jan 25, 2023
Lovely product, arrived reasonably fast and we'll packaged!
Freak
Jun 14, 2022
Trinity Hydeman
Feb 7, 2022
Troy Yohe
Feb 3, 2022
This came with good instructions, though I did need to do some research on my own. Worked for my purpose. I was able to cover the bottom of a plastic tub for a pottery wet box.
inkyhopper