Discolouration of light timber by adjacent dark timber during sanding and finishing.

[PenMaker22]

Hi Everyone,

I sometimes make pens with glued sections of timber. One that I particularly like is, for example, maple bands in ebony, or vice versa. However, I often find that the darker timber discolours the lighter timber, making it beige or, even worse, just a dirty grey colour.

Does anyone have any tips to prevent that happening?

Cheers.

 

[flexi]

Is this when sanding??
I have used loads of segmented blanks and once the glue is dried they are very stable....the only way they discolour is very fine dust from sanding and a quick wipe down with boiled linseed oil generally removes it....
Hope this helps

 

[Penpal]

Care with CA and light sanding help reduce the carry over, Welcome to the forum Scott.

Peter.

 

[Margo]

I've read (somewhere!) to use sanding sealer between each and every grit when sanding to reduce discolouration.

I've tried it, but only once!

 

[Pierre]

Hi Everyone,

I sometimes make pens with glued sections of timber. One that I particularly like is, for example, maple bands in ebony, or vice versa. However, I often find that the darker timber discolours the lighter timber, making it beige or, even worse, just a dirty grey colour.

Does anyone have any tips to prevent that happening?

Cheers.

Hi Scott and welcome,

Are you using wet and dry? Many people advocate wet sanding, I have never found this to work but I do tend to work in the spring/summer where my temperatures hit up to 42 degrees so wet sanding can drag staining. Equally some glues take more than 24 hours to dry even though they may be classified as 15 mins 30 mins 2 hours etc I let all of my glues dry for at least 24 hours and sometimes 2 days because they also can allow dust drag into the lighter wood, ie the glue is still damp and sticking to the dust. Actually it goes into both woods but you cant see it so well into the darker wood. Finally, some glues can take the stain in the darker wood and by osmosis into the cells they can transfer the pigment, so you need to control the glue. For wood on wood I use normal PVA white, for wood on pen tubes I use gorilla (but that is hidden) and for wood on aluminium I use medium CA and let it cure for 48 hours. I have found that using yellow PVA can give the appearance of pigment transfer but in fact it is the PVA that is causing the colour change, but I haven't used that in the last 5 years so they may have changed the formula over time.

Dont forget that some dense exotic woods have their own oils like lignum vitae and azobe or Niangon and these oils themselves transfer their colour but that can be overcome with a drop of acetone (yes one drop on a cloth for a pen sized object more for a bowl) to remove the surface oil because the discoloration is only on the surface. With these types of oil, they are a bit greasy like coronavirus, so I would think that a drop of alcohol (Ie same strength as hand sanitizer 60% proof) would work as well; use it as you would a sanding sealer. (note I havent had to try that yet but logic comes to mind from a past life in biological stuff).

 

[Bill Mooney]

As Margo says, sanding sealer before sanding with each grit stops the dark timber bleeding into the light timber. I always do it without a problem.

 

[Penpal]

SAnding sealer can help for sure.

Peter.

 

[Phil Dart]

I'm with the sanding sealer advocates. Also, a tack cloth will help to remove contaminant dust from the grain

 

[Margo]

So here's a kind of related question - can grubby, red-stained tack cloth be revived?

 

[Phil Dart]

No, but I find that tack cloths tend to keep their dirt to themselves. As long as there is still a bit of "tack" to it, it should still do the job. You have to take a reasonable view about it though - if it's filthy you'll need to replace it.

 

[Neil]

Easier solution, don’t use sandpaper.