Can you put clear varnish over semigloss paint?
Yes, however, if it is an oil-based clear you'll see an amber color to the tint. Water-based clears tend to be crystal clear and do not affect the underlying color.
There are flat paints that are made to go over semigloss paint. Many inexpensive flat paints will peel almost immediately when laid over semigloss. The most common solution is to roughen the surface of the semigloss (sandpaper, sandblasting, steel wool, or trisodium phosphate). The actual requirement is to remove alkyds which migrate to the surface of some semigloss and gloss paints. The alkyds make it impossible for latex or acrylic to bond to the surface…
Yes, Spar varnish is a marine quality exterior varnish that can be used over many surfaces, however it does have an amber hue that will affect the color of whatever surface is being coated. If you're looking for a long-lasting crystal clear coating then a better choice would be a water-based polyurethane coating.
You can paint matte paint over semi-gloss paint as long as they are the same base, i.e. oil over oil, latex over latex, or oil over latex and the surface is clean and dulled either by sanding or chemical deglossing. If the semi-gloss is oil and you are painting latex matte, then use an oil based primer as a bridge first.
Paint can be applied over varnish, but it needs to be a compatible type of paint for the type of varnish, and the surface needs to be prepared by removing loose material, dirt and sanding. If it is not a compatible paint the surface needs to be etch primed. Contact a local paint supplier for advice.
If you are painting over a semi gloss paint you wand to use trisodium phosphate or TSP on the wall before you start painting. This is a deglosser that will allow whatever paint you are using to adhere to the wall. tip: After using TSP on the wall, give it a soap and water wash to prevent the phosphate in TSP to cause mildew/mold damage.
No it will cause big problems. You should sand down to paint before adding a new coat of clearcoat Answer: There is nothing wrong with putting a new coat of clear over old, as long as it is well sanded , and the underlying clearcoat is in sound condition. It is necessary to do it when spot- repairing a clear -over- base metallic paintjob.