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| Finishing, The Final Touch Wood is a porous material constructed of hollow cells and pores through which the plant’s water and nutrients travelled when the tree was living. In order to produce a durable surface which is resistant to dirt and wear and enhances the beauty of the wood, it is necessary to seal the cells and block the pores. There are several ways of doing this. The earliest attempts at finish just used wax. This patinated well and produced a sheen but had no durability and tended to pick up and hold dirt . Drying oils such as Linseed were used and were better than wax, but only just. From the drying oils were developed various varnishes and these began to really protect the wood. Shellac used as “French polish” lacks durability. French polish is extremely labour intensive and although a superb finish can be obtained, as it is soluble in alcohol, damaged by moisture and not particularly hard wearing, it is no longer a practical finish for most uses. It is worth noting that although “French polishing” came into use during the 19th century , table tops were still varnished as polish was just not up to the job. It is interesting too, that polish was specified for use in public buildings and embassies etc. by the British “Ministry of Works” , as then was, because of the ease of repair. I only use French polish to touch up repaired items in my own workshop. Some woods, such as beech and maple, are so fine grained that they have no apparent pores and can be finished without worrying about filling the grain. More porous woods may not need to be filled depending on the look required. Oak, for instance, finished with a matt lacquer can look very natural with its grain showing through the surface of the finish. Woods such as rosewood or mahogany, however, really need to be filled. The first method of filling the grain of a timber is with paste filler. This is a thixotropic material which is rubbed into the grain of the wood and rubbed off across the grain leaving the pores of the wood full. After a light sanding the finish is applied in the normal manner over the top of the filler. The material can be “clear filler” which in this case means probably a light cream colour , or it can be “stain filler” in which case it is coloured a suitable shade for the work in hand . One can use the material of the finish itself to fill the grain. Most finishing materials shrink as they dry so they tend to leave the imprint of the wood’s pores on the surface. Apply the material to the bare wood. There is no need to worry about getting the surface to a silky smoothness at this stage. I rarely go above 100 or 120 grit on bare wood as the first coat of finish is always very rough when it dries, and the very fine almost polished finish produced by very fine sanding can cause adhesion problems. Once the first coat is completely hard , sand it down to the bare wood. I use 180 grit, lubricated finishing paper here, and now I get a silky smooth finish. The material will have tied the surface fibres together. Now give subsequent coats sanding with 240 grit paper in between. When you have a good full covering with no pore marks in it, then flat down with about 320 grit paper and apply the top coat. My preference now would be to denib (lightly sand to remove any dust specks) and then produce a sheen by carefully rubbing with very fine wire wool (000 or 0000) in the direction of the grain, and then giving a wipe over with furniture wax to take the dry look away. This not only looks good to my eye, it feels wonderful. If I want a brighter finish , I go on from there with various rubbing compounds.
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Staining Staining and colouring wood is something I have always discouraged. Where possible use a wood of the colour you want. This isn't always possible so you are sometimes faced with the need to stain or colour . There are several methods of colouring wood. Water stain. This is a simple and cheap method but it isn't always so easy to obtain the materials.. The main material I use is “Vandyke brown” This comes in the form of brown powder and is good for producing a really good dark oak finish. Water stains have the advantage that as water isn't a particularly good “wetting agent” It goes on very evenly and doesn’t soak in much more in some places than others. .There are other materials available but sometimes not easy to obtain in small quantities. The Usual sort of oil stain available in several different colours is easy to use but can produce a quite uneven colour and is often quite disappointing,, There are some materials now that are like the oil stains but water based.. I find these a little muddy in appearance but much more even than the oil ones . Another way of darkening some timbers .. Notably Oak is to “Fume “ them with ammonia fumes. I usually make a plastic film tent over the item although if the thing is small enough I have seen a cardboard box used. I then place a tray of domestic Cloudy ammonia solution inside the tent and leave for an hour or so.. .. Be careful as inhaling the fumes can be dangerous and very unpleasant. watch the work as it can become very dark in deed. Usually the colour is not too dark and fairly even. This is not a suitable method for refinishing as there is always likely to be finish residue in the wood that will prevent even colouring . The preceding methods are applied to the bare wood before any finish is applied.. However colour can be added to the finishing material it self and coloured varnishes and laquers are available.. care must be taken to minimise brush marks and a better finish is usually obtained by spraying .. PAGE UNDER CONSTRUCTION Please send any quieries about this subject to me. |