Microscale Solvent

I've used MicroSet and MicroSol since the 1970's and never had a bottle of either stuff that was thick.  You may have gotten a bad batch. 

As for the white stain, I've sometimes had it leave a sort of whitish residue after it dries, but normally it can be removed with a q-tip dipped in the same solution.  If that doesn't work, then there must be something more sinister going on.

I look at decaling as the final step that can go disastrously wrong and ruin a model and all the work that went into it.  It's nerve-wracking, so I've taken to use the solutions (especially MicroSol) very sparingly--just enough to get them to do their jobs.  And they don't always work out even then.

Hope you can get things fixed up again.

i've used microset on hasegawa and tamiya decals with no problem. i will NOT use microsol on tamiya decals though.

The blue bottle is MicroSet which should be less aggressive than the red (MicroSol). It should also be thin and watery. The blue bottle smells vinegary, whereas the red bottle has a very slight ammonia-like smell. I've not known MicroSet to be thick at all.

Though you can't really rule it out, it's unlikely to be an age related issue, as the bottle of MicroSet that I have is at least 25 years old and still works fine.

MicroSet doesn't usually leave any noticeable residue. On the other hand, MicroSol has been known to sometimes cause hazing on acrylic finishes (including Future) particularly if the base has not had sufficient curing time (as opposed to drying time). Normally, when this happens, an overspray with a clear glosscoat will eliminate the hazing. 

Yeah, that's it blue bottle.  I'm using Hasegawa's decals, but this kit doesn't look that old.  It had new decals in it for VS-21

blue bottle as in their setting solution? what decals were you using? i know that microscale isn't friendly with all decals or at least micro sol.