Can walnut stained veneer be lightened?

You will have to sand off the existing finish.if you would like to re-stain them

Since veneer is a fine layer of wood ....I would use a palm sander but sand it lightly an get it as light colored as u can ....or I would use a rag with laquer thinner on it wipe a section an sand it .....laquer thinner is great for removing paint an stains .....

Unfortunately a dark stain stays dark. You will only be able to apply a darker stain.

Good Luck!

Yes Paint them any colour you like, by using a Multi Surface Primer! or Stain them even darker. But to do that you would need to rub them down to remove old varnish finish.

Try a light sanding then a thinned paint that is closer to what you want.

I'm a very experienced painter an I have lighten dark stain ....it is a little time consuming but if u want to put a lighter stain on it u have to sand the dark stain off .....it's just like refinishing true oak hardwood floors...

Try a product called Orange Glo. It will slowly clean old dark varnish.