stain under epoxy

I am about to wrap a plywood (luan) kayak with epoxy and glass, to be finished mostly bright, but I would like a little darker tone. Will using an oil based wood stain cause a loss of adhesion for the epoxy? This is more of a knockabout boat than a work of art so I dont want to get too carried away with the finish in respect to time and expense. Thanks for your help, Chris

 

After reading and getting a fair knowledge of the 2 types of wood stains. I would try to go with the water based dye stains for a job that is to be epoxied later. Water based does not seal the wood as well as oil. Surf the web for oil and dye stains. You can then make a decision.

 

Take a piece of scrap and test the color after a few coats of epoxy without staining first. Luan will darken up considerably with an application of epoxy. You may find this is a color you can live with. Epoxy will add a slight amber to the color and it will need varnish to protect from UV so even more color will be going on. A quick test of the color can be done with some spirits wiped onto the surface of the bare wood. This will be very close to the color of the wood after epoxy.

Most stains available in Lowes/Depot or similar store will seal the wood, which isn't the best way to get epoxy to fill and stick to the fibers of the wood. A pigment can be added to epoxy, but will require some experimenting to get the color you want. I'd add the pigmented coat after the raw wood has had an straight epoxy coating first.

 

I'd tend to agree with Richard, the water based dye type stains should work fine.

You will have to insure that the wood is then completely dry prior to putting on the epoxy, you most certainly don't want to seal in excess moisture.

Bill H.

 

Any oilcontents in the stain will cause later on delamination. Epoxy will only work if the wood is absolute free of any greasy contents. An ammonia based stain could do the job, although as PAR says - epoxy and varnish will darken the luan considerably. I woul follow his method to check on required color.

 

Thank you for all your replies. I am going to try a water based stain on a test piece. I had already done a test piece with a couple of shades of stain and also bare wood. This is what gave rise to my concern, the bare wood absorbed a great deal more epoxy than the stained areas.It looks as though I have some time to kill before I can lay the glass due to the temperature so this will give me something to do without resorting to actual household chores. thanks again, Chris

 

Clearly the stain is sealing the pores of the wood if the epoxy isn't soaking in as much compared to unstained areas. You want the epoxy to penetrate as much as it can. I use techniques to increase the epoxy's ability to penetrate wood, not decrease it. If you use epoxy in this fashion, you're basically using it as a rather expensive paint or varnish. Without the penetration into the fibers of the wood, cloth set in the epoxy will likely delaminate very quickly with the movement of the wood, through use, stresses or moisture content changes.

 

The absorbtion problem I observed was with the oil based stain. I have just applied some water based stain to a test piece and will apply some epoxy this weekend and will watch the absorbtion characteristics then. By the way what are the techniques that you use to increase absorbtion (if not proprietary). Thanks , Chris

 

The bottom line for sheathing a hull is the best stick and penetration you can get. Any stain will limit the amount of adhesion the epoxy and entombed cloth will have on the hull.

Since you seem married to the idea of stain first, maybe you should log onto www.WestSystem.com and read about their on line techniques and methods. Maybe ask them what they think, or if you prefer, the manufacture of the brand of epoxy you intend to use. They are the industry leader and offer a great deal of advice and free methods manuals.

My techniques for increasing bond and penetration will not work if you seal the pores of the wood with something.

Have you tried just pure epoxy? What is the main issue you have about it? The amount needed? The color?

 

I should tell you there are really 3 types of stains. Oil-- water-- and a rarely used, solvent dyes. Solvent dyes are a industrial ink. very toxic but extremely thin in viscosity. More in the Ether and alcohol class with a fine colored powder that needs to be shaken. It stains very fast and dries even faster. When dry, the pores of the wood are almost unchanged. BUT. It requires a full resperator and the correct filter to stop cancer of your liver. Some printers use it for very high speed presses.----------A simple test of the epoxy, is to strike the surface of each sample with a hammer lightly. The good one stands out.