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From: rdp@teddy.UUCP
Newsgroups: net.rec.wood
Subject: Re: Bleeding Knots!
Message-ID: <2261@teddy.UUCP>
Date: Thu, 13-Mar-86 10:31:30 EST
Article-I.D.: teddy.2261
Posted: Thu Mar 13 10:31:30 1986
Date-Received: Sun, 16-Mar-86 00:32:39 EST
References: <872@hercules.UUCP>
Distribution: net
Organization: GenRad, Inc., Concord, Mass.
Lines: 18

> I have some old pine chests that were bought unfinished (about 10 years
> ago).  They were stained and varnished for many years.  About four years
> ago, I sanded them down to the wood, and painted them with white oil-based
> enamel (PPG).  Now I have a problem with the knots bleeding through as a
> brown discoloration (this takes a few months to show up after painting).  
> I have repainted them twice now, with the same results.

The recommended technique for painting over knows is to first paint the knots
themselves with shellac, maybe two or more coats, then, after the shellac has
dried, paint the rest of the cabinet. The various constituents of the sap in
the knot (like crude forms of turpentine, and the like) can easily bleed
both oil-based and latex paints, but an alcohol-based coating, such as shellac,
seems to cure the problem. 

I have used this technique successfully even on outdoor trim, with no bleed-
through after several years of exposure.

Dick Pierce