Making an Oil Varnish

[Ted Boscana]

I have built a reproduction of a 17th Century New England Court Cupboard. I have cooked 20 or so batches of BLO and Colophony (pine rosin) trying to find the proper ratio of oil to rosin. My last batch had a weight ratio of 1 to 2 1/4 ,oil to rosin, and it feels like it is still pretty soft with an open time of about 4 hours. I am trying to reproduce this historic varnish, but I feel like I am reinventing the wheel. Does anyone have any experience with making a simple brown oil varnish?

[Rich Engelhardt]

Hello,

My last batch had a weight ratio of 1 to 2 1/4 ,oil to rosin, and it feels like it is still pretty soft with an open time of about 4 hours

4 hours is extremely quick.
I suggest switching over from boiled to raw oil.
That should get your open time up to a few days - or longer.
Add pure gum turps for a drier.

You can also check to see if any of the art supply stores in the area stock Copal.

I'm really pressed for time right now or I'd go into a lot more detail.
I'll get back to this ASAP - probably later tonight.

In the meantime google "carriage varnish".
There's several good descriptions of the ingrediants used.

Also -noting your location - Williamsburg - is this a restoration where matching an orignal is required or is is a reproduction, where simply matching the appearance is required?

[Steve Schoene]

My books are all somewhere still in boxes, but I can recall two sources for such recipes. Jeffrey Greene American Furniture of the 18th Century has some of the old recipes in an appendix.

The First American Furniture Finishers Manual, a reprint edited by Robert Mussey is another source.

Both of these should be available at the Visitors Center bookstore at Colonial Williamsburg.

Of course you have another resource in Williamsburg. That is the conservation department at Colonial Williamsburg. They are about the only guys around that might have real experience with Old Brown Varnish.

Frankly, that brown oil varnish didn't have a very good reputation and wouldn't likely have been used on high end furniture, I don't think. You may actually be seeing what the product was like. It's an interesting project to be sure.

[Ted Boscana]

I work for Colonial Williamsburg as a joiner and I built this piece and presented it at our 2007 woodworking conference. The problem I am having is that when you work from period recipes there is a certain expectation of experience, so while these recipes are very forthcoming with ingredients they lack much in the way of proportions expecting that the maker using the recipe has made a similar varnish before. I have got to get back to the shop, I've got visitors to talk with and I get back to this later.

[Steve Schoene]

I see the problem. I've played with spirit varnishes a tiny bit, but never with the oil varnishes.

I was about to say I doubted few had made such varnish, but then I thought of violin makers. A google on violin varnish reveals that there are a bunch of varnishmakers using natural resins and traditional techniques. It even looks like there is linseed/rosin varnish made for sale. I suspect you could get a lot of info from some of these guys, especially if you used the auspices of Colonial Williamsburg.

I also came across a DVD on making a basic oil varnish! Who would think it.

http://www.violins.ca/books/books_dvds_flores.html

[Ted Boscana]

Thanks for the link, I will see if our little museum can get a copy.

[Rich Engelhardt]

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