Varnish provides a method of protecting wood as well as highlighting the beauty of the grain. With coloured varnishes, it is also possible to modify the appearance to blend with other woods. This can be particularly useful where a softwood has been used and you wish to give the appearance of a hardwood such as oak. But take care, as with dyes, that you do not allow the varnish to be ‘double-coated’ at the joins in your work.
Old varnish
If the wood is already varnished and this is in poor condition, use varnish remover to strip the old coating first.
Remember, as always, to follow all safety instructions.
Preparation for varnishing
Prepare the wood thoroughly. It should be clean, free from grease and smooth. Sand thoroughly finishing with a fine grade of paper. Note that sanding across the flow of the grain will leave scratches which, whilst they may not be visible yet, may become exaggerated when the varnish is applied.
Choosing varnish
There are a vast number of different varnishes available and the final results will depend on many factors – the number of layers, the type of varnish, the type of wood and any previous coatings as well as the application.
Making a sample board could be very beneficial, particularly if you are using a coloured varnish. It will let you see exactly the final effect. Choose an offcut of the same wood used to make the item, or if that is not possible, try to find a piece which is the same type of wood and of similar colour. Apply a coat of varnish to the sample and allow it to dry. If using coloured varnish, experiment with different numbers of layers.
Application
The method is very similar to that used for painting.
To seal bare wood, apply a coat of varnish diluted with about 10% of the recommended solvent. Allow to dry and apply a further two coats of undiluted varnish. If your sample shows you that you only want one layer of coloured varnish for the desired effect, use clear varnish for the sealing coat and topcoat.
Solvents can be harmful. Always read the label and follow the safety instructions.