Mortar components should be measured and mixed carefully to assure
the uniformity of visual and physical characteristics. Dry ingredients
are measured by volume and thoroughly mixed before the
addition of any water.
Sand must be added in a damp, loose condition to avoid over sanding.
Repointing mortar is typically pre-hydrated by adding water so
it will just hold together, thus allowing it to stand for a period
of time before the final water is added.
Half the water should be added, followed by mixing for approximately
five (5) minutes.
The remaining water should then be added in small portions until
a mortar of the desired consistency is reached.
The total volume of water necessary may vary from batch to batch,
depending on weather conditions. It is important to keep the water
to a minimum for two reasons:
- first, a drier mortar is cleaner to work with, and it can
be compacted tightly into the joints;
- second, with no excess water to evaporate, the mortar cures
without shrinkage cracks.
Mortar should be used within approximately 30 minutes of final
mixing, and "retempering," or adding more water, should
not be permitted. .