I am currently doing a small retro plastering job ("retro" because I am in the U.S.). I am mixing masonry sand with lime plaster. The way I do it is make a homogeneous mix of sand and lime while both ingredients are dry, then add water only when they are mixed well.
I am curious how bad it would be to cut the corner of mixing it twice (once dry and once with water) and just dump water on top of the unmixed sand and lime, then mix only once. Will that cause unmixed lumps of lime surrounded by solid lumps of sand?
Best Answer
Dry mixing all the ingredients before adding water ensures a complete homogenous batch. Mixing dry allows you to see how complete the materials have combined. Proper blending of the mix is necessary in order to produce a strong and workable mortar.
Of course if you are using a powered mixer you would just shovel in the proper amounts as it is turning and add the correct amount of water. No need for dry mixing.