Sealing Pine Resin and Sap
Here's a tip for chemical surface treatment to harden sap and resin, preventing or reducing bleed-through. May 18, 2010
I am getting ready to spray a knotty pine kitchen with MagnaMax. Will a sealer coat of Vinyl help keep the rosin from bleeding through? We have stayed away from knotty pine for years till now. I know shellac is the only thing that will for sure stop the bleed through, I just wanted to stay MLCampbell compliant.
From contributor Y:
Vinyl's will not stop the initial action nor the long term action of the sap/rosin effects. What you can do though is this: treat the wood with a 5% solution of phosphoric acid. This will bring all the resinous matter to the surface almost immediately. Wipe this down with methanol immediately a couple of times. This reduces the resinous matter to an unsoluable state that will be non reactive to the coatings. You also can get most of the sap off the surface first if it's real bad with den-alcohol before the PA treatment, let dry and proceed as outlined if you do. Then apply a good wet coat of 1 lb.cut dewaxed shellac let dry well and apply your vinyl over it without sanding the shellac. Let dry, sand as normal, and apply your top coats. If you want make samples of vinyl over the bare wood without the shellac and compare the two and decide what you want to do. I know vinyl direct without this treatment will not hold up but I'm blind on whether or not it will if done without the shellac since I have never done it.
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