Hi everybody, 

I ve been playing with grey cement in my GFRC mix and I wondered if you guys have been having issues with colours on countertops you have made? 

I tend to use CEM 1 grey cement to all my mixes and when demolding everything looks fine. It s only after sealing  that colour pops out; slabs may look yellowish/greenish. 

Do you use white cement+ pigment  in your GFRC mix in order to make a "clean" grey slab ? Doesn t the grey turn a bit blue-ish ? 

Is my cement just not grey enough ? 

Can the sand I use cause any colour variations ? I usually just take the milky surface away with a wetsander (200 grit)...

 

Thanks for helping ? 

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anything and everything can cause slight color variations - temperature, how long you waited to lay in your backer coat, slight variations in water content - the list goes on . embracing and working with these subtle variations and differences rather than trying to control them is key. 

Moving to a good white cement and using pigment to create the gray helps you control the tone of the gray much better. years ago Buddy Rhodes took samples of gray cement from all over the US and found two distinct tones of gray - a warm and a cool tone. - used at varied loadings these are how we create our "cement colors" - the are by far and away the most used pigments. 

Yes, grey cements vary from plant to plant and batch to batch.  For a true grey use white cement with pure black pigment.

Thanks guys for your help!  I m gonna start making my mix with white cement ....

I get a nice subtle purple when I add pure black to white cement.  Very cool shades of gray. 

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