General:
The natural beauty of wood is enhanced by the application of clear varnish, which can be used on both soft and hard woods. However, no clear varnish system on wood will stand up for any length of time if the surface is fully exposed to weather. Ultraviolet rays from the sun penetrate the transparent varnish and destroy the structure of the wood causing loss of adhesion and subsequent flaking. Varnishes containing transparent pigments which are U.V. absorbers, are the only varnishes that should be used on exterior exposed natural timber.
Preparation:
New:
Clean to remove dirt, plaster splashes, etc., rub down smooth with sandpaper and dust off.
Previously stained, varnished or lacquered:
If in poor condition, remove all existing stain, varnish or lacquer with Dekro Super Paint Stripper or a strong washing soda solution (1kg per 5 litres warm water), and steel wool. Wash down with vinegar water (1 litre vinegar to 5 litres water) and bleach to a uniform colour with a 10% Oxalic Acid Solution. Neutralize with domestic ammonia, rinse with clean water and leave to dry. Sand smooth and dust off.
Note:
- Oxalic acid is highly toxic.
- Light woods such as maple and birch cannot be treated as above.
- After the above treatment the wood must be absolutely dry before coating.
If in good condition, wash down with sugar soap and water, or solvent to remove dirt, grease, wax polish, etc. Rub down smooth with sandpaper to a matt finish and dust off.
Previously waxed:
Wash down thoroughly with Dekro Wunda Clean or suitable concentrated detergent to remove all traces of Wax, rinse and allow to dry thoroughly. Rub down and dust off. Do a test patch to be sure all wax has been Removed before coating the whole area.