Hello
I have been painting with Tamiya acrylics heavily thinned with Tamiya thinner with great results. my problems start at the decal stage. I airbrush Vallejo gloss varnish first then apply decals with micro sol/set then airbrush Vallejo satin varnish. The decals still seem to silver, and even come off during the weathering stage, not to mention the clogged airbrush. In the past I have had good results using Tamiya X22 clear as a way of providing a good surface for decals and as a good sealer for weathering, but I have heard that x22 should not be used as a varnish as it is an additive to make flat paint gloss. Basically I need a good gloss and satin varnish that will help with decals and will not clog my iwata.
Any advice would greatly assist me. Paul

I roughly do and was doing that same things you are but I never came across your results.

I have used tamiya X-22 clear as a top coat before applying decals and washes. The problem I've had with X-22 is that it takes a very long time to really cure (maybe 5-7 days) and I get the same performance with gunze sangyo acrylics as well. The gunze clear is supposed to be the same as the blue mr. hobby top coat spray can Other than that, the decal and weathering process remained the same.

I moved to using vallejo varnish since it seemed to give a much stronger coat with less overall curing time. The only difference that we have is that I go straight to satin varnish, then let it dry overnight, apply decals, set, then hit it with satin varnish again. I find satin varnish enough to provide a surface smooth enough for decals so i skip the gloss. Make sure you give ample time to let it cure. I also use the varnish without thinning.

What weathering medium do you use? I assume it is enamel based and not acrylic or lacquer. Always shake the vallejo satin varnish well (if you think you've shaken enough, shake 2 times more . For tip dry I think you could put a few drops of retarder but I haven't tested that yet. I'm in a very tropical country and I haven't encountered tip dry on the varnish, the primers however, are a different story.

My take on your silvering might be because of the difference of the coat under the decal (gloss) and the coat on top (satin). If you really want to go with this route I guess you could try this
1. Gloss Coat, dry
2. Apply decal
3. Set, dry
4. Gloss Coat on decal area, dry
5. Satin coat overall

Also some things to keep in mind.
1. Do not use X-20A thinner (or alcohol based thinners) on any vallejo paint or varnish, its a recipe for disaster. (except for polyurethane based products but I haven't tested it thoroughly)
2. Tamiya X-22 clear is basically a clear coat/paint. What you mentioned about using it to make flat based paints gloss is not entirely true. The best it can do is reduce the flatness but it will never give a gloss finish similar to non-XF paint unless you really dilute it and end up with a very low pigment paint. Best I could do was turn it to satin finish. The flat clear and semi-gloss clear can give a gloss paint a flatter finish but if you want to make it flat, use the tamiya flat base instead and it won't dilute the paint too much.

Basically you can go from gloss to flat but almost never the other way around.

As FYI, Tamiya X-21 Flat Base is the additive to get a finish from gloss to flat. It comes in both acrylic and enamel so just make sure to get the right one to match your need. Cheers

If X22 was working for you, why bother changing? I'd just go back to what you know worked. Seal the decals with more gloss afterwards, before hitting the flat or satin.

I don't like Vallejo paints - they are finicky in the airbrush, and rather "soft" when brush-painted, needing a hard clear sealant to keep them from rubbing off. If you need to use a non-Tamiya acrylic gloss, I would recommend Micro Gloss from Micro Scale - I use it over Tamiya with no trouble. They also make Micro Flat & Micro Satin, which give good hard surfaces for weathering.

The silvering is usually a problem with trapped air pockets under the decal, which suggests the underlying gloss surface wasn't sufficiently glossed to start with. Matte paints break up the light with a microscopically "rough" surface texture that traps air in all the nooks & crannies, while gloss surfaces are smooth. You need to make sure whatever gloss you use is applied well enough to fill in those nooks & crannies, or silvering will occur. Of course, you might also have issues with Vallejo adhesion over Tamiya, or even a reaction between your weathering products and the Vallejo.

I worked with Micro Sol for a long while, and always had hit or miss with it.

Finally I tried Mr. Mark Setter and Mr. Mark Softener and never looked back its amazing to work with