Finishing Techniques for Blotch-Prone Wood

      A cabinetmaker who uses a lot of Alder gets some advice on finishing the wood without creating a blotchy appearance. June 18, 2013

I own a busy cabinet shop, and currently send all my product out for finishing. The main species we use for cabinets is alder (it really is a beautiful and under-valued material). However our last two finishing shops used have had severe issues with blotching. I'm hoping to move the finishing in-house to help speed up turn-around times, save expenses, and for control quality.

I've been doing a lot of reading online and there is a lot of conflicting info. Between wash coats, sealers, glue size, dewaxed shellac, toners, thinned dyes, and on and on so Iím pretty confused. If anyone can share a wiping/gel stain based finishing and topcoat system that would work on alder, cherry, and maple consistently and prevent blotching I'd be most appreciative!

Forum Responses
(Finishing Forum)
From contributor G:
In order to prevent blotchiness we use stain base (clear) from ML Campbell and we stain the whole job with that. After dry (30' or so) we stain with the pigmented one (if you go that route). You are going to get a little lighter final color, but you can correct that living the stain a couple of minutes before you wipe it off or using a toner coat. Then we use Kristal sealer and top coat from MLC, or self-sealer water white CV from SW. Watch your sanding schedule and donít rush the finish.

From the original questioner:
So you are in effect using the clear base as a sanding sealer? Are you wiping or spraying this?

From contributor G:
That clear stain base before the stain process is just to avoid blotchiness in cherry, soft maple, alder and species with that problem. The only thing is the final color is going to be a little lighter unless you ask your stain supplier to make the stain formula stronger.

From contributor F:
All methods used to control blotching will have their pro's and con's. Using a clear stain base to do this is simple and more forgiving than using a wash coat but it is not as effective or reliable. It generally will reduce blotching on most woods but it does not completely eliminate it on any woods in my experience so results can be less than consistent.

Using a gel wiping stain in conjunction with a clear stain base is probably the best way to go for someone with limited finishing experience but beware it may not be the cure all that you are hoping for and it will limit your choice of colors to what is achievable with this method.

A typical finish schedule of this type would be as follows:

1. Sand to 150-180 grit.

2. Apply clear base as you would if you were staining the wood, wipe on and let penetrate a few minutes and then wipe off the excess.

3. Before the clear base gets a chance to completely dry, apply the stain in the normal fashion.

4. Proceed as normal with sealer/topcoats.

Another thing that should be noted is that not all clear stain bases will work the same way. Generally speaking ones that have a higher solids content will be more effective as a stain controller. You should also do some testing and consult manufacturers to ensure product compatibility.

From contributor B:
I've been staining alder with great results for years. I would recommend not using pigmented stains as they are more prone to blotching. I use dyes and dye/pigment stains. You can shoot on a lighter color of dye than your intended color and add some color to your sanding sealer and topcoat to get to your color of choice. Or you can build your dye by doing multiple coats and then just shoot clear over it. On light colored jobs I'll just use one application of straight dye. Doing it that way you'll highlight the grain and still have nice overall even color.

From contributor F:
Contributor B brings up a good point. Dyes are the way to go for alder and other blotch prone woods, but maybe not for a newbie finisher. Many newbie finishers have a bad experience with their first attempt at spraying dyes because no one has showed them the right way to do it, they spray it at too high a strength and get inconsistent colors and color streaking in some spots while not enough color in others.

This all can be avoided with a bit of knowledge and practice so if you decide to go that route make sure you get a good tech rep to show you the right way to mix and spray dyes as they can be a fantastic tool when used correctly. They are much more forgiving when diluted to a weaker mixture and applied in multiple coats with low air pressure.

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