- Borax is commonly added to gypsum products during their preparation primarily because it functions as a retarder.
- The setting reaction of gypsum involves the hydration of calcium sulfate hemihydrate to form a solid matrix of calcium sulfate dihydrate.
- Without retarding agents, this setting process occurs rapidly, which can limit the working time available for manipulation of the material.

- The addition of borax slows down the crystallization process by interfering with the growth of gypsum crystals.
- This extension of the setting time allows for better handling and molding of the material before it hardens.
- Therefore, borax helps in controlling the working time rather than enhancing the strength or hardness of the final product.

To summarize:
- Borax acts as a retarder in gypsum products.
- It slows the setting time by delaying crystal growth.
- This leads to a longer working/flow time without negatively affecting final strength.
- It does not directly enhance strength or hardness of the set cast.

Understanding this role is vital for practitioners who require adequate working time for precise impressions or molds in dentistry and other medical fields.