Shelf Life of Behlen's Rockhard Varnish

[Brett Bobo]

What's the shelf life for Behlen's Rockhard varnish? I used this on a previous project about three years ago and the remaining concentrate was stored in a sealed glass jar ever since. Granted, it's been stored in a cabinet away from sunlight but in the elements since my garage shop is not conditioned space. The stored concentrate appears to look fine, e.g. no gumming present, but I'm not sure if that's enough of an indication to use it.

My plan was to use the same finishing schedule as before since this will be a complementary piece in a bedroom. As I understand it now, the latest version of Rockhard uses uerthane resin, not the previous phenolic resin, so I can't buy new a like-for-like replacement. Otherwise, my plan was to switch to Waterlox original sealer/finish to avoid any potential issues of using the old varnish and to have a comparable result. In case it makes any difference, my plan is to spray either varnish--maybe there could be atomization issues with an older varnish.

Thanks in advance,
Brett

[Steve Schoene]

I'd be leery of varnish that was three years old after having been opened. Your odds are better that it is OK if there was zero headroom in your glass container and if the Rockhard was put in that container directly after the can was initially opened, and not after you had finished applying varnish originally.

Additionally I would be quite concerned about trying to spray oil based varnish unless you have a very strong professional grade spray booth to remove overspray and prevent bounce back and also leaving a sticky crust on the entire area in which you are spraying. Varnish just dries so slowly compared to more commonly sprayed materials.

[Andy Pratt]

Behlen's rockhard has a very short opened shelf life in my experience. I had some two year old cans (factory sealed) that I opened recently. I knew they were getting close to being too old so I opened, used and immediately resealed them with that oxygen displacing spray. It was fine for the first coat and I made sure to get a good seal on the can but had lots of problems with it gumming up on every subsequent use. This same thing happened with three cans in a row (used them up one coat at a time getting my subsequent coats done), so it wasn't an isolated issue.

After that experience I stopped using rockhard, which i really liked, as the cost and frustration wasn't worth the risk/hassle.

When I have compared identical pieces that had (new) behlen's rockhard and minwax oil based poly on them I couldn't tell the difference, so I would just go with that if you are looking for a visual match, and chuck that old rockhard. 3 years is too long to risk on a project in my opinion. Before I stopped using it, 1 month from opening a can to using it was my rule, if it was any older than that I threw it out.