Some mortar or mortar mix changes color after it completely sets. For example, when it's mixed, it's gray & changes to white a couple days later. Is there a way to know which is which?

 

yes - whatever you bought will act as you post'd,,, try some different materials such as 1 might buy from a REAL masonry supply house,,, when we repoint, we use colored water by tinting w/sher-wms pigments

 

I wasn't complaining about the change from gray to white. In fact, I think the customers would prefer it. I was wondering if there is a way to know ahead of time, if a change were going to take place.

 

Most masonry supply stores usually have small mortar color charts, showing what the cured color should look like if mixed properly. Big box stores, not likely to have such charts.

 

The color of the sand will also make a difference. I was on one job where they had to tear down a lot of newly laid brick because the homeowner picked a colored mortar but there was miscommunication over which sand was to be used. I suspect minute differences in the sand would also make minute differences in the mortar's color.

 

Color of sand does become a bigger factor as mortar or concrete ages. The surfaces of sand are coated by the mortar paste that wears off as it ages.

Also, pigment lightens up (fades) as the concrete cured and they are subjected to UV and moisture. Any concrete will lighten as it cures. Natural pigments will always fade and can be more variable. Synthetic pigments (highly purified and fired at various temperatures depending on the color) are usually used in most colored ready mix and concrete products because it is more consistent. Site mixing with synthetic pigments is very difficult, if not impossible due to the small batches and methods for a synthetic pigment the is very highly loaded with pure pigment that almost act like a bomb going off.

Trying to match the appearance of mortar made from pre-packaged mortar mixes (sand, cement and pigment) using site materials (local sand, bagged cement and possibly lime) is difficult because the job is nor necessarily in the same locality as the job. - Many prepackaged mixes are made from materials many hundreds of miles away and different cements.

There is always the old "seat of the pants" method of mixing a trial batch, spreading some of the "cream" on a finger nail and blowing on it to get a rough idea fo what it might look like.

Dick

 

That's good info. Thanks.
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