I have been doing a lot of decorative concrete around my house, and I have yet to find a masking tape or caulking or anything that can hold the acid stain where I want it. I finally found something that I think will work, it's a gel that makes the stain thicker and keeps it in place. This way you can just paint it where you want it. The problem is that it is not sold in the colors that I want. So, does anyone know what I could add to an acid stain to make it thicker like that?
Modello Gel-lo is a thickening agent for liquid coloring mediums such as acid and water-based stains for concrete. The addition of Modello Gel-lo allows for more controlled color application and helps to reduce "wicking" of the stains under the edges of the Modello patterns.
And Stain Mule™.
Stain Mule will thicken both acid stains and water based colorants. When color placement control is necessary, the Mule is your product.