Final answer:
When mixing gypsum, it is important to use the correct amount of water and powder. If additional powder is added after mixing has begun, the mix will be inconsistent.
Step-by-step explanation:
When mixing gypsum, it is important to use the correct amount of water and powder. If additional powder is added after mixing has begun, the mix will be inconsistent.
Gypsum is a hydration reaction in which water is added to calcium sulfate dihydrate (CaSO4 · 2H2O) to form calcium sulfate hemihydrate (CaSO4 · 0.5H2O). The correct water-to-powder ratio is crucial for this reaction to occur correctly. If additional powder is added after mixing has begun, the ratio will be disrupted and the resulting mix will not have the desired properties.
For example, if you are using gypsum to make plaster of Paris, the correct water-to-powder ratio will ensure that the mixture sets and hardens properly. Adding more powder after the initial mixing will create lumps and uneven consistency, making it harder for the mixture to set uniformly.