Recently did a 3/8 minus open terrazzo with a 1% load of green pig. Due to my lack of work space I usually cast half a kitchen at a time. This last project I had to cast an adjoining piece out of the second batch. The color turned out to be way off. I suspect the sedimentary sand to be the issue as the bags for that batch turned out to be contaminated with tiny chunks of clay. I'd like to stick with this sand as the varying particle sizes give the surface a nice look. Is there a way to wash sand to insure a close color match batch to batch or should I be going a different route?

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I'm sure this has be gone over before but a search for prior threads turns up a gazillion results. Anybody have a good link to this topic?

Often times in this case its not the sand that causing the fluctuation in color but rather the type of portland you are using. Especially grey portland. Batch to batch may not be truly the same color, throwing off your color. Also look at your curing regiment. How much heat did you throw at the piece when covering. Did you use the exact same method when you cured. Sometimes all these variables can be exact but the slightest thing can throw the color off just enough to not get a perfect match. Best way to combat this is too cast conjoined pieces all at once. Hope this helps.

Yes I did run gray but it was the same gray(3) 94lb. sacs that I cross blend in my bin from the first batch. I was unaware that cure time can shift color. I'll have to make several samples out of one batch and see whats happening as I pop each one over a period of a few days. Hmm.

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