Head Cements

I just sat down at the tyin' table and found that both my clear and black head cements
have practically dried up. I had noticed that the clear appeared to be evaporating,
but didn't realized that it had lost it's liquidity (don't know if this is this even
proper use of the word). Both cements are hard or at the very least too thick to use.

Is there any thing that I can do to reconstitute the cements--paint thinners, varsol?

Mark --who should, obviously, sit at the tyin' table more often!--