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Certain climatic conditions make the use of Calcium Chloride necessary, however- the following procedures must be adhered to.
Recommendations are as follows:
Never use more than 2 lbs of CaCl per bag of cement in the plaster mix.
Whether liquid, granular or flake CaCl is used, it must always be completely diluted in water prior to addition to the plaster mix. Do not allow any undissolved granules of CaCl to be added to the mortar.
These recommendations are in line with those outlined by the National Plasterer's Council Technical Manual and take into account the possible detrimental effects of either too much Calcium Chloride or concentrated calcium chloride being introduced to a plaster mix. These effects include:
Possible fast set of the plaster resulting in cracking and crazing.
Potential chemical reaction between the pigments and the calcium chloride, thereby creating pigment highlights or "starbursts" in the finished plaster.
For the occasional addition of CaCl to plaster mixes including IPC Integral Plaster Color, we recommend the following procedure based on a mix incorporating 4 bags of white Portland cement, Type 1 in a 6 carbonate to 4 cement mix:
Add approximately 20 gallons of water.
Add 4 bags white cement.
Add 300 lbs (3 bags) of Pool Mix/aggregate and mix until lump-free.
Mix 1 gallon bottle of IPC Integral Plaster Color liquid colorant to 1-2 gallons water in an empty bucket. Rinse residue from bottle with additional water and add to bucket. Add entire bucket of pre-diluted IPC Integral Plaster Color to mixer. Blend until fully dispersed.
Add rest of Pool Mix/aggregate (300 lbs).
To an empty 5 gallon pail add CaCl (liquid, flake or granules) and 2 to 3 gallons of water.
Fully disperse or dissolve the CaCl in the bucket.
Add diluted CaCl mixture to the mixer.
Add any additional water needed to reach desired consistency.
NEVER use the following mixing procedure.
IPC Integral Plaster Color
This mixing procedure will result in clotting of the pigments and subsequent dark streaks in the plaster. The CaCl and IPC Integral Plaster Color should always be added at separate stages in the mixing process.
Note: A practical guide to determine the volume of dry granular CaCl is: