How should mortar on the board be kept until it is used?

Keeping mortar on the board sprinkled lightly with water helps maintain its moisture content and workability. Mortar is a mixture of cement, sand, and water, and it requires moisture to remain workable for a longer period. If mortar dries out, it can become too stiff or hard to apply effectively, which could compromise the quality of the work. Lightly sprinkling water periodically can help prevent this drying out, allowing for more time to use the mortar without needing to remix a fresh batch.

While covering the mortar with plastic could serve to retain moisture as well, it's crucial that the mortar still retains some flexibility. Simply covering it may not ensure proper moisture retention without the additional hydration provided by sprinkling. Storing mortar in a cool place does not address moisture retention directly, and mixing it with additional cement would not only alter its consistency but might also weaken its bond strength rather than enhance it. Proper moisture management is essential for ensuring that the mortar performs correctly during application and curing.