cement colourant with ordinary cement?

I thought portland was ordinary cement, OPC. Colouring pigment works with all cements, but if you want pale yellow or cream you'd need to start with white cement.

NT

cements, but if you want pale yellow or cream you'd need to start with white cement.

White cement and building sand gives you yellow, without colouring. Some building sand has quite a lot of (natural) surpless pigment.

I had a holiday job in the 60s, with a chap who was pointing the stones on historic buildings. My job was to wash the sand to remove bright colours. barrow, hose in bottom, getting wet all day long. Fantastic job. I loved it.

Any that did not go grey we returned to the builders merchants, and they brought us something else.

snipped-for-privacy@care2.com wrote in news: snipped-for-privacy@googlegroups.com:

Thanks for this. My cement bags say Lafarge general purpose, which I thought was different from Portland, but clearly you are right.

I'm not sure whether it's 'wholly' Portland, though:

So this is the wrong stuff? If I used some yellow colourant with it, would the result be greyish yellow (which would probably be OK), or would something else go on (as it might for example with some art paints, where chemical properties can prevent application of standard colour-mixing rules)?

Thanks again!

Harry

Cement dyes are normally iron oxides, which are pretty much chemically inert I would have thought. A little goes a long way and can look garishly bright

All cement is made to a standard unless you sneak some in from furrin parts. The only thing you might watch out for is some has additives that make it much darker than the traditional stuff.

Ordinary cement IS Portland cement. And white cement is only tad more than grey..

cements, but if you want pale yellow or cream you'd need to start with white cement.

Yellow dye won't have any efect on dark green/grey cement, you'd have to use white cement, which is about a tenner a bag. Also you'd need white or very pale sand for the dye to have the desired effect. And you'll need a hell of a lot of dye to achive any kind of colour per mix, that is, if you are adding it to the mix rather than adding it to the laid concrete, at least a kilo per 25kg of cement.

Red's a different kettle of fish, it goes a lot further and you can get red sand which sort of meets you half way.

As with all pigments, a lot depends on the quality of the dispersion. I went overboard with the yellow when patching round a manhole cover. Bright yellow :-)

yellow + grey = a warmer tint of grey

NT

in theory yellow adds brightness, red adds warmth

"Phil L" wrote in news:ei1as.97409$ snipped-for-privacy@fx27.am:

Thanks for this. I've already bought the standard cement.

Do you think I could get away with buying a bag of white cement, mixing it with a lot of water and some yellow colourant, and then doing a cement wash?

Or can you only do cement washes on walls?

The area I'm doing is in a front garden and only gets occasional foot traffic.

Harry

It would work. Temporarily. I'd lay the bulk in grey, and a top layer with white. Lay the 2nd before the 1st is fully set and they'll bond as one.

NT

On 01 Oct 2012, you wrote in uk.d-i-y:

Thanks for this. What thickness would I need for the top layer?

Harry