Testing wood for stain

[QTOFFER]

Is there any way to test how evenly a piece of wood will take a stain before staining it?

My dad did a fretwork portrait that looked great until he stained it - two areas simply wouldn't take stain and left noticeable light streaks. He wound up painting the piece. The BB plywood was evenly sanded with 150 grit after the pattern was removed. This was either an invisible defect in the wood or perhaps a manufacturing artifact.

So, if I were to wipe the piece with mineral spirits, would that reveal any areas that would be resistant to stain?

[MacS]

Testing the wood?

Wiping the wood with a solvent will show the woods color after it is coated, it may not show you how it will look after it is stained.

Woods will take dyes and pigmented stains differently, and then again not all all stains are exactly the same. Dye stains are not intended to be wiped, because they dry to fast in most cases, they should be sprayed. Pigmented stains should be applied by wiping, brushing, or spraying, but then the pigmented stain must be wiped dry.

Some finishers first use wash coats, which is thinned out shellac, boiled linseed oil, or a glue sizing to seal the wood before they apply their stain, these coatings act as a barrier and prevent the stain from penetrating deep into the wood, preventing or reducing blotching.

You should try making up some samples using this barrier technique whenever your in doubt. (I do)

Think Twice, Finish Once

https://www.macsimmons

[sawdustus]

blotchy staining

Andy,
If you have or can get it, Bob Flexner's book Understanding Wood Finishing published by Rodale has a wealth of information. So does Perfect Wood Finishing by Sue Noble published by Popular Woodworking Books. Glue residue is a major culprit for uneven absorption of stain but for many woods, it is also due to the differences between heart and sapwood or early and late wood.

[MacS]

Heart And Sapwood

I would think Andy father, and other scrollers would know the differences between the lighter sap and the darker heartwood, and on the dried glue, if he left the glue on his pieces I'm sure he would know it was the glue..

The sapwood is the outer section of the tree, the heartwood is the older and darker part of the tree.

See photo enclosed.

[QTOFFER]

Thanks for the replies!

The whole piece was thoroughly sanded after pattern removal, so I'm sure it isn't glue residue. It looks like it may be knotwood.

What's particularly annoying is that this denser area did not look different from the surrounding area prior to finishing.

So my question is: Can you tell just by looking that a piece of wood will contain steaks after staining?

[GrayBeard Phil]

Andy:

I want to focus on Baltic Birch Plywood and the Fretwork your father did.

This is my experience, YMMV (your mileage may vary.)

True Baltic Birch (as opposed to just Birch plywood) has a problem with blotchy dye absorbtion when cut as fretwork. Fretwork exposes all kinds of end-grain and side-grain on the top veneer. Thus, a small exposed area could be end-grain to end-grain and absorb an extra amount of dye by capillary action of the end-grain cell walls. While another small area could be side grain to side grain, and absorb a lot less because the end-grain has less exposure to capillary action absorbtion. This end-grain capillary absorbtion is on the walls of the kerf.

If you have a solid scrap piece of that plywood, apply the stain, or dye, to the whole piece of scrap. Then compare the end results to your father's work. Notice the edges of the piece of scrap vs the middle of the plywood. The edges, where the end-grain is, should be darker (for about 1/16 inch in from edge,) and the lightest should be in the middle well away from any edge. If you cannot match up the colors of your dad's project to the scrap, well, this problem (end-grain absorbtion) does not apply to your case.

It is my personal experience not to dye BB plywood to fretwork. The only time I tried it, it was just as your father experienced. All kinds of blotchy due to end grain absorbtion. I just might try to apply a dye before cutting, but the urge to try that never bit me. Dyes are just too messy.

Phil

[MacS]

Staining the wood.

Andy,

I think you answered your own question, if you father did not see the problem when he was selecting the wood, and while he was scrolling the piece, and then during the finishing of the piece .Then I am sure that others would not have seen the problem neither.

Some defects in the wood can be adjusted before finishing, while other problems are better left until the end of the normal finish where color adjust can be better for overall color.

Andy, there are no guarantees in any ones advise, not even in books, magazines, or on any forums. I do the best I can to help with the questions, I hope in all cases I do help.

https://www.macsimmons.com