Plaster #1 Moulding (50 Pounds)

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Plaster #1 Moulding (50 Pounds)


An ornamental plaster used for creating decorative trim or running cornices. Designed for use where expansion control, hardness and strength are not primary considerations.


  • Often referred to as Plaster of Paris or soft plaster, No. 1 Moulding Plaster is used to create waste molds or temporary patterns where surface hardness and strength are not crucial. No. 1 Moulding Plaster:
  • Offers a controlled set that provides uniform workability
  • Has a fine grain — making it ideal for producing sharp detail when used neat for cast work
  • Complies with ASTM C28
  • Sets in 27-37 minutes after mixing
  • Requires 70 parts water by weight per 100 parts plaster
  • Is available in 50 pound bags

DOWNLOAD usg-no-1-moulding-plaster.pdf

USG No. 1 Moulding Plaster
Often referred to as plaster of Paris or soft plaster. 

How to mix Plaster:

1. Always weigh out the amount of plaster you need, then look up the water by weight percentage. For example USG # 1 Moulding for making stuff, uses 70% water to plaster. So 10 lb. of plaster requires 7 lb. of water. First weigh out the plaster you need, take that amount and multiply it by .7,(point 7), (7/10) this gives you how much water to use.

2. Generally speaking the larger the percentage of water the softer and more absorbent the plaster will be. The harder the plaster the less water used.

3. Hot water will speed up the set time and cold water will slow it down.

4. Place the water in a suitable sized container. Always add plaster to water. Pour the plaster into the water and let slake for one minute. Mix by hand or with a Jiffy Mixer, being careful not to suck air into the plaster. When the mixture is lump free it is ready to pour; don?t wait for it to start to thicken.

Warning WARNING: This product can expose you to chemicals including Silica, crystalline (airborne particles of respirable size), which are known to the State of California to cause cancer.  For more information go to