Gypsum is a mineral that is crystal-like in appearance. It grows in a thick bed that is associated with that of the sedimentary rock. An ingredient in drywall, gypsum is used as a construction material. It is also an ingredient in plaster of Paris, which is used to make casts. Aside from the ones mentioned, gypsum has a lot of commercial and industrial uses.
Water for Mixing
In mixing gypsum, water that is at room temperature must be used. The ideal temperature for the water would be around 70 degrees Fahrenheit. Clean water must also be used so that dirt will not get mixed in with the gypsum. It will be easy to spot dirt on a gypsum surface because of its light color.
The water has to be added to the gypsum powder gradually to avoid putting too much into the mixture. The gypsum must be allowed to soak in the water before mixing. Too much water will thin out the gypsum, making it very difficult to use. Less water in the mixture makes it more durable when it is used as cement or a plaster.
Mixing Techniques
When hand-mixing gypsum, mix it in a back-and-forth motion while turning the container every once in awhile. This will allow the gypsum to be evenly incorporated with the water. The sides of the bowl must also be scraped to make sure there is no dry gypsum sticking to the sides. Continue mixing until an even consistency is achieved. There should be no lumps in the gypsum mixture.
To blend the gypsum mechanically, mix it at high speed for about 10 minutes, depending on the amount of water and gypsum used. It may take longer to mix if a large amount of gypsum and water is used. The gypsum and water must first be mixed by hand for a short time before being placed into the mixer. This is to make sure that all the gypsum is dry. The dry gypsum will fly off in all directions if it is placed directly on the mixer.
Use Immediately
After mixing the gypsum with water, the resulting slurry must be used within two to three minutes. Gypsum when mixed with water tends to dry up really fast. It is best to have the molds ready so that the slurry can be poured into them immediately.
Only small amounts should be mixed at one time to prevent hardening and only make enough to use at that moment. Mixed gypsum cannot be saved for later projects because it will harden. It is also good to mix the gypsum next to the area where you will apply it.
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