Hello S&B --- Try the link below. It is to an old post that contains a couple of color product charts I put together a while back. You will have to scroll down until you find the message that contains the direct links to the documents (one a web link, the other a Word doc.), but I think you may find them helpful if you are new at working with colorants. Hope they help.

tango

Here is a link that might be useful: Color Charts Post Link

Thanks Tango. That's probably more info than I'll ever need! I'm looking at a chemical, or acid or mineral, surface stain just so it looks a little less like a badly cast lump of concrete :) I'll try and get some photos to see what happens. I have some iron sulphate and that seems like a good place to start.

NO professional work just for my own yard. Have used wood stain with varying results, there is an oil type residue that is left, and the stain seems to be pretty light. I found it most effecive for light staining. Have used oxides designed for pottery, mixed into the dry mix becomes an intregal color for your mix (tufa, concrete, cement based mixes)Oxides color for color do not mix like paint, black oxide and red oxide make purple. the dry oxides should not be more than 10% of the amount of cement in your mix. Have played with acid etch stains. I like many of the acid etch stains. The AES require some follow up to STOP the etch, either with doses of water or an ammonia water mix, plus always good ventilation and a mask. My experience with the AES is that the color changes when you add a sealer over the stain. I think the color becomes much more intense and rich.
Definitely a 'cast lump of concrete' is a good way to experiment.
Add some color, happy casting,
dena

Different pigments can get radically different results depending on their type. The man made oxides are quite different from natural ones.
I know my red and black don't make purple, I wish they did.:)
The 10% rule is just a standard set for legal purposes in the construction industry as some pigments can degrade the concrete strength if too much is used.
I have used much more than this for little stuff.
But it would get costly for big stuff.

A potassium permanganate solution is offered as a way to "neutralize" the high pH of concrete or hypertufa troughs. Proportions I have seen is 1/2 oz. crystals to 3 gallons water, soak 24 hours. I have always wondered about the staining capabilities.