I have some satin black enamel paint, after applying it I found it to be too glossy. I know you can make paint more glossy, for example by adding varnish to it, but is there a way to make it less glossy?
You can coat it with a satin clear finish. or even a matte finish. Both are available at most paint stores and big box stores.
Use steel wool or plastic abrasive pads on it (after it's dried.)
There are also "paint flattening agents" if you are looking for a chemical/additive fix for another coat.
For the best possible results, just go buy the same paint in a less glossy firm and repaint the wall. All the other solutions will take as much time and still might not give the results you want. Save time and effort and just repaint.
TSP has been used by painters for many years to "de-gloss" paint.
I have used it to both flatten a painted rooms glossy look, as well as to provide a surface that a new top coat can adhere to.
Gloss enamel needs to be cut (a surface tooth) established for new paint to adhere. If you do not provide a tooth for new paint it can peel off of glossy enamel (a lesson learned for me long ago).
I had that same problem (oil based paint too glossy). 000 steel wool worked, sanding worked, tsp had no effect, vinegar had no effect. I mixed some talc (baby powder) with my oil based high gloss paint and was able to get the flat appearance I wanted. I found that it took a ratio of about 6 parts paint to 1 part talc to get the desired result
The 2 answers you have amount to (i) roughen it, and (ii) satin/matte varnish it.
I suggest doing both. When you're applying one finish on top of another, neither of which is primer/undercoat, you need a good key -- hence roughening the surface. You don't want to create visible scratches though. At some point you want to leave it in a warm place for a couple of days to make sure it's completely dry. Then wipe over with methylated spirits to remove dust/grease. Then you can apply your top coat. Be sure to use a product with the same base as the paint you've just put on -- a water-based finish like acrylic varnish won't stick well to fresh oil paint.
You could of course -- if you're buying something anyway -- get a satin paint for a last coat.
Add a small amount of talc (try 2 TBSP per gallon). Try painting it on a small piece of wood to see how it looks. Add more or less depending on the results.
Buy some zinc and add to your gloss finish enamel paint and mix it In this way you can make in matt enamel
Old trick given to me by old coach painter was add talc to the oil paint Soaks up the oil in the paint dulling it.
Be careful with what Making It Matt suggested. Don't add to much or it goes gritty rough.
Rub glossy paint on dry wall with hand sanitizer (Walmart Equate brand) on a paper towel. It will remove the gloss, super fast, super simple. No sanding, no matte clear coat. Just wipe.
For liquid paint that you want to dry with less gloss, add diatomaceous earth. Available as swimming pool filter supplies. Talc might work but I believe diatomaceous earth is used by paint manufacturers. You would need to experiment to find how much to get the affect you want.
Just wipe it with vinegar. There will be no more gloss. Try in an inconspicuous spot first to see if you like the result before going any further.
If you have the time its best with the proper grade of sandpaper/steelwool, to sand between coats or alternating coats. Experimentation is a great learning tool. At a mere cost of your time and some money.