Try not to purchase “quarts” …
… if at all possible , unless you need that much for a job. Better to get “pints” , especially for small jobs like paddles . A pint goes a long way , even with three coats , there’s quite a bit left over …
HPS = High Pressure Sodium
In my shop at work, where I occasionally play.
Jim
Good article on varnish.
Thanks for the link.
The thick varnish dried OK, and was sndable, so I assume that tomorrow morning I will find a dry, nicely coated paddle. Ready for another (thinned) coat.
N.T. - great idea for overbrushing with turp. It would have saved me a heavy sanding.
Jim
McMaster-Carr to the rescue!
http://www.mcmaster.com/ page 1658
4, 8, 16 oz cans available. Cases of 12.
Mike and Dave, if you guys want I can order a case and we can split it 3 ways or 4 if N.T. wants in. Delivery at Raystown?
Jim
No thanks…
I was surprised to find quarts of oil based Cabot spar varnish at the local Lowe’s. I’ve gone through a quart in a month and like the results. It is somewhat slow drying, but worth the wait. They also now have Watco Teak oil. Pretty unusual to find this stuff at Lowe’s.
bloxygen
Does wonders for preserving unused varnish. I’ve had one too many 1/2 full cans of varnish polymerize on me. I especially recommended for tung oil based varnishes that seem to polymerize quicker than I can use them.
That’s been my experience, too
I’ve had really good results with Bloxygen.
No, you really can’t “revive” varnish…
…that’s begun to cure in the can. Varnish doesn’t dry, it cures by combining with oxygen, which is why having air in a varnish container causes it to partially cure. The problem is that cured varnish is chemically different than uncured varnish and is will not dissolve in the same thinners. You can thin it, stir it and disperse the partially cured portion into the rest, but as you found, you end up with a thicker, gloppy varnish that doesn’t flow well. When varnish gets to that point, it’s best to toss it. I hate doing that for several reasons, but it beats having it ruin a finishing job or having to sand it endlessly.
Good news and bad news
Good news is that the thinned varnish did dry overnight. Bad news is that it still didn’t flow properly, and even with the very runny appearance it didn’t tip-out well. Guess I will be chucking it.
The paddle is still quite usable, but all of the other kids will probably point to me and laugh. But then, they already do that.
Live and learn.
Jim
Can size?
What is the consensus on size?
16 oz?
8 oz?
I can order either.
Jim
Purge the can with an inert gas?
Could you fill the empty area of the can with something other than air to get the oxygen out of the can before sealing it?
We use argon and nitrogen at work, I have no idea what’s available to the average citizen.
How old is your turpentine?
Turpentine may lose some of its potential as a solvent if it’s stored in an oversized container for long periods. These issues involving less-than-fresh finishes really only apply to hobbyists, as any pro would never consider using anything that’s been allowed to sit for long.
Old-Timey painter’s trick
was to take a breath and exhale into the top of the can of oil-based paint before sealing the lid.
Jim
Satin
Sounds to me like you may have a can of satin varnish which has solids in it that sink to the bottom. These solids are what make the varnish satin. If you stirred it and the goo disappeared, I would suspect there is nothing wrong with the varnish, it’s just not a gloss varnish.
Well, varnishing season
is rapidly ending (temps below 60-65) and I have no other projects on the horizon. I will wait until spring and then buy a new can. ANd decant it into smaller cans.
Jim
My thoughts
If the varnish was full gloss there should not have been settlement. If the varnish was satin finish the fillers or extenders used to reduce the gloss may have settled.
The increase in viscosity was caused either by loss of solvent due to evaporation or reaction with oxygen causing polymerisation. If the former add some white spirit, if the latter (and this will be apparent as the varnish will also have particles of semi cured product) throw it away as it will not as good as fresh varnish in appearance terms.
Any can of varnish will give ageing problems if the level is less than 2/3 in my experience.
One trick we used to use when storing airdrying products in the laboratory where I worked was to turn the cans upside down (ensuring the lid was secure, this meant the void then above the liquid became saturated with solvent vapour which prevented oxidation & also eliminated any solvent loss from the can lid. Again this was only useful when the can was more than half full.
Alternatively as mentioned decant from a large can into smaller ones for storage.
White spirits vs. mineral spirits
On this side of the pond, what you call “white spirit” is unavailable to most hobbyists. At work, I buy “Stoddard’s solvent” from a specialty supplier which, I believe, is what you mean. Or are “white spirit” and what we call mineral spirits (odorless paint thinner) one in the same?
Please allow another query. Why would turpentine be a less desireable choice in this case?
Thank you, Cockney, for your unvarnished response.
The problem isn’t the turps…
…it’s that partially cured varnish won’t dissolve in turps or mineral spirits.
Good trick!
Storing the can upside down that is. Makes perfect sense.
The varnish was a satin product. I used only a small amount before resealing the can, carefully wiping the groove clean before pounding the lid on with a rubber mallet. But at least two years have gone by, so it’s life-span was pretty much gone as far as I am concerned.
Jim
What means ‘tip out’ ?