QUESTION

Darken Grout - How can you darken grout lines. I dont want to use a paint or stain. Someone at Home Depot said I could use half mineral spirits mixed with half linseed oil to darken the lines. Is that true?

ANSWER

ANSWER - The only legitimate way to alter the color of grout is to use a product manufactured and warranted for that purpose. 

If you do not use a product that is manufactured for this purpose then you are doing it at your own risk.

There is grout colorant which is painted onto the grout to stain and seal it.

Historically surface type sealers can be applied to grout that will darken it and seal it.  Penetrating sealers normally do not darken the grout.  There are sealer enhancers that intentionally darken stone that would likely darken grout.

I have heard of using linseed oil, but I understand it never dries and can become a maintenance problem.  I have heard that in Mexico they use diesel fuel to stain their porous grout and tile.  Obviously these types of products have fumes and can be dangerous.

Good Luck!