Uneven coloring before applying varnish, not related to the grain pattern

[jeanlucb]

Hi!

 

I have watched the "A simple varnish finish" video multiple times.  It's very informative but I'm stuck with a problem that's not addressed in the video.

 

I'm close to finishing my first furniture project, an entertainment center.  The grade A red birch veneer plywood is in really good shape so following the advice of many, I decided to just give it a light hand sanding with 180 grit paper before varnishing.

 

Some of the boards have darker bands that don't match the wood pattern.  Light sanding does not seem to make much difference.  What causes this?  Can it be fixed?  I'm tempted to sand more but really don't want to sand through my very thin veneer layer.  It's possible that it would go away when varnishing but the look I get when cleaning it up with mineral spirits seems to indicate that it won't.

 

Have you seen this before?  What can be done?

 

Thanks!

 

Jean-Luc

 

[wdwerker]

Blotchy grain is kinda typical in the red birch I have used. I usually stain it and then use a sprayed toner to even out the color.

Have you seen any of the videos on blotch control ? Some folks swear by them.

[Guest]

Do you have any large scraps on which you can test different finishes?  It is really the only way to know for sure what will work.   It is either blotch in the wood (which is common in birch and cherry), or it could be part of the glue layer showing through the thin veneer. 

 

An oil-based varnish will definitely highlight the blotch.   A water-based finish or shellac will not highlight it as much.  If you are staining, a gel stain does a nice job of controling blotch. 

 

Like wdwerker said, some people swear by blotch control.  Check out Charles Neil's website.  He sells a proprietary blotch control that gets good reviews (I have not used it).  He has a reputation for being responsive, if you send him an email with your concern he will probably get back and let you know if his product is appropriate. 

http://www.cn-woodworking.com/

[jeanlucb]

Thanks for the advice.  I'll look for a scrap that's big enough to do tests on.   I was planning on using Arm-R-Seal and no tinting.  I think that's oil based.

 

I was not aware of blotching before your replies and will definitely keep that in mind for my next project when selecting wood!