Plaster question

Thickness.

The cementitious surface coating should have an average minimum ‘thickness’ of ⅜" and an average maximum thickness of ¾".

Though some fluctuation may exist across the cementitious surface coating, most of the cementitious surface coating thickness should remain within these tolerance levels.

Small areas of highs and lows, spanning no more than several inches in diameter per occurrence, are allowed an additional
tolerance.

This would include the filling of small holes, pits, or dig-outs (indentations around plumbing fixtures or lighting fixtures) in the substrate.


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Thank you for all the information. Very helpful indeed.
 
Thickness.

The cementitious surface coating should have an average minimum ‘thickness’ of ⅜" and an average maximum thickness of ¾".

Though some fluctuation may exist across the cementitious surface coating, most of the cementitious surface coating thickness should remain within these tolerance levels.

Small areas of highs and lows, spanning no more than several inches in diameter per occurrence, are allowed an additional
tolerance.

This would include the filling of small holes, pits, or dig-outs (indentations around plumbing fixtures or lighting fixtures) in the substrate.


View attachment 588570
Thank you again. Along these same lines, how much plaster thickness on average can I expect to lose with an acid bath (non pool draining). Just average, I know there's no way to predict. And how much plaster life is forfeited with an acid bath?
 
Assuming about 1,000 sqft of plaster, 10 µm is 89 oz of plaster.

1 µm is 8.9 oz of plaster.

158 oz acid = 10 µm (micrometers) loss of plaster thickness or 89 oz of plaster.

1 gallon of acid removes about 8 µm of plaster or 71.2 oz (4.45 lb) of plaster.

10 gallons of acid = 80 µm of plaster = 712 oz or 45 lbs of plaster.

80 µm of plaster = 0.00315 inches
 
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Note that even though the loss is thin, the difference in roughness can be quite significant because the surface is not evenly removed.

The aggregate is left exposed and this is a significant reason to avoid acid washing whenever possible.

The surface can be like sandpaper.

When you account for the aggregate, the loss of surface will be about double the predicted amount.

1 gallon of acid removes about 16 µm of plaster or 71 oz of cement and 71 oz of aggregate for a total loss of 142 oz or 8.9 lbs of plaster.

The acid only eats the cement, which exposes the aggregate quartz or pebble and the aggregate falls out.
 
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Note that even though the loss is thin, the difference in roughness can be quite significant because the surface is not evenly removed.

The aggregate is left exposed and this is a significant reason to avoid acid washing whenever possible.

The surface can be like sandpaper.

When you account for the aggregate, the loss of surface will be about double the predicted amount.

1 gallon of acid removes about 16 µm of plaster or 71 oz of cement and 71 oz of aggregate for a total loss of 142 oz or 8.9 lbs of plaster.

The acid only eats the cement, which exposes the aggregate quartz or pebble and the aggregate falls out.
Well, so much for an acid bath. I guess we just learn to live with the discoloration and random black specks in the white plaster?
 
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