The Acid Test
Before varnishing a surface, get rid of unsightly dark water marks on stripped surfaces with an application of oxalic acid.
Wear protective gloves and eye protection. Make up a solution with boiling water and apply it to the mark with a brush.
Once the stain has disappeared, neutralize the surface with distilled white vinegar. Check for any differences in the wood’s colour while the surface is still wet and apply stain as necessary.
Wiping the surface with a cloth dampened with mineral spirits will provide you with a good idea as to how the surface will look when coated with a clear varnish finish.
A Test in Time
How Dark Will It Be?
Another problem with stains is that you need to be sure of how many coats you need to apply to get the result that you want. So, get an off-cut of the same timber used for the item that you are staining. Draw four or five lines across it and number each. Now apply successive coats – the first to the whole length, the second (once the first is dry) from position 2 onwards, the third from 3 onwards and so on. Now you’ll know exactly how dark the coats will be.
Easy Removal
The cleaner the surface, the better the result. An easy way to remove every tiny speck of sawdust or dust from a surface is to use a tack cloth. Dip a piece of mutton cloth or any other lint-free cloth into turpentine and then put a few drops of varnish onto it. Knead it a bit to distribute the varnish and then wipe the surface clean in long sweeps from one side to the other.