I am new to PCB making. I bought some UV curable soldermask from the store and it was lying around in a black container for a few months. I decided to test it with a strip board but it has got thick and gooey. Is there any suitable solvent for thinning it?

And can I use Acetone as a thinner?

 

Do you mean Etching mask? if so, bin it, even the stuff in aerosols tends to thicken up after being left on the shelf for to long. the nozzles are pretty useless too. I now buy the presensitized boards, success every time!