Factors to be aware of before varnishing:
Are conditions suitable for vanishing? Temperature is, probably the main factor to consider when deciding to vanish. The surface to be varnished should be, if possible, between 70 and 80 degrees and surely not below 60 degrees. Heat is necessary to sure make the varnish brushes and flows correctly. The varnish itself should be warm and almost the same temperatures as you are able to get it. If the varnish has been chilled during transporting or storage, don’t use it until the temperature has been raised by placing the can in a pail of hot water, about 110 degrees F or by letting the can stand near, not on, a hot radiator a day or two if you can. If at any time the varnish has been at zero degrees, even if it was for a few hours, there is some likelihood that some of the gums or driers have solidified. Then the varnish should be warmed up and put through a double thickness of cheese cloth before using. Otherwise you may have a case of dodgy, sandy varnish when it is brushed on to the surface. Consider which type of varnish you want to use. The two main choices are acrylic and polyurethane. Acrylic is quick drying and odour free. Polyurethane is harder wearing but smells strongly when you apply it. It is a good idea to apply your varnish when it is quiet so that there is less likelihood of vibration caused by others walking through the room or building, raising dust.
Firstly thin the varnish before you apply the first coat (there is not need to thin varnish for the second coat) for best results. Measure a small quantity of varnish into a measuring container. Make a note of the volume and pour it into the paint kettle. Next, measure about a tenth of this volume in water (if you are using DIY shop, you can make one by dipping lint free cloth in white spirit. Immediately brush on the second coat of varnish, before dust has a chance to settle back onto the surface. Apply the varnish along the grain, then brush across the grain to make sure the bands have blended. Finish off with light brush strokes along the grain. It is almost impossible to achieve a perfect finish once the varnish has set hard, so feel for any imperfection with your fingertips and rub them gently with a pad of fine wire will dipped in wax polish.
Check the wood to see if it needs to be filled before varnishing. If it does need to be filled, buy wood filler that will match the colour of the finish. Fillers are made in a restricted colour range, so look at the filler colour chart in the shop and choose the nearest. Don’t match the wood against wet filler as it will become paler as it dries. You can also take a piece of the wood you will be painting to help you decide. To avoid creating bubbles in the varnish, don’t scrape the loaded brush against the rim of the tin or across a string tied across a paint kettle; instead, just load your brush and then tap the sides of the container with the brush. The excess varnish will drip off the brush. If the wood looks too shiny after varnishing, you can reduce the sheen with fine wire wool. Rub gently, with the grain, to cut back the gloss so that there is hardly any reflection at all. This is particularly suitable for pale woods. Commercial dip-stripping in hot caustic soda is a quick and easy way to remove layers of paint from moulded doors and leave a bare wood finish suitable for varnishing. Not all doors are worth stripping, so test one before paying for a whole set; also, joints may become loose and doors may warp, so check with the company that your doors are suitable. If you wish you can mark each door with a chiselled Roman numeral in the top edge to keep a note of which door belongs with which frame.
About the Author:
Anayo Keane-Etumnu is an expert tradesman. He writes about DIY and Plumbing and Heating.