Combining the best of two wall paints can create a look that is easier to clean and shines a little bit brighter. Flat paint on its own creates a matte look, with layers that can look like velvet. Its finish allows you to cover any imperfections in the wall, but the downside is that it is harder to clean. Satin paint shines, like the name implies, with a glossy finish. It can withstand a scrubbing with soap and water, but the shine highlights the imperfections that the flat paint can hide. Put the best of both together to make something that is easy to clean and thoroughly covers scrapes and scuffs.
Match The Resins
Paint compatibility is the main rule to follow. Mixing a latex flat paint with a latex semi-gloss paint will allow you to mix a usable new sheen. Mixing a latex paint with an oil will not. When purchasing a new gloss to add to your flat paint, check to make sure both paints contain the same resins. Interior paints mix with interior, not exterior, paints. Just like oil and water do not mix, neither will flat paint and a non-compatible sheen.
Semi or Gloss?
Mixing flat paint with a higher gloss paint creates an intermediate finish. Satin paint is a higher gloss, so to get the look of a satin wall with a flat paint, you'll need a semi-gloss or a gloss sheen. Semi-gloss can be cleaned with soap and water, and will not have the blinding sheen of a pure gloss. Choosing a compatible and matching semi-gloss can provide a subtle result that looks like satin. Gloss sheen is the shiniest paint and is best for trim work or areas that need to stand out. When mixed with flat paint, it may not be the best at hiding imperfections and some users warn that it can cause streaks if not mixed well with the flat.
Stir and Stir Some More
Flat paint is a coarse product, which means that any additional paint added to it will need to be thoroughly mixed to attain the best result. Start with the flat paint as a base and pour half into a 1-gallon bucket. Gradually add the semi-gloss sheen and mix. You can always add more sheen, but you can't remove it, so start small. Note the amount you are mixing together, as this will help replicate the color in the future if more paint is needed. Once you've stirred into a uniform mix, stir it again for good measure to ensure a smooth application. Use a small amount in a test patch of wall and wait at least four hours before applying any paint over the test patch. If the test patch is your desired sheen, go ahead and paint the walls. If not, add more semi-gloss to the mix to increase the sheen level.