Varnishing Wood, How to Varnish Wood
Instructions and tips on varnishing wood, how to apply varnish to wood surfaces.
¶ Generally speaking the varnishes of today are far superior to any supplied to finishers of other times. They are as nearly fool proof as science and remarkable manufacturing facilities can make them. They will produce remarkably beautiful finishes and durable finishes if used skillfully and under reasonable conditions of service. The wonder is that they behave so well and prove so satisfactory when used as they are under adverse circumstances in the building field. The furniture finisher and automobile painter have learned the reasonableness of, and necessity for, providing correct surfaces and surroundings fit for varnishing. It is easier for them to do so than for the finisher in the building field, because they have the work brought to their shops, whereas the house finisher must take his shop to the work. That is probably the fundamental reason why the finishing 4one an furniture and vehicles has always been far superior to any other. And still the house finisher is to be congratulated upon producing as fine finishes as he does, considering the adverse conditions under which he must work, The best he can do is to keep in mind what the perfect conditions for varnishing are and then do the best he can to approach them.
¶ Conditions Suitable for Varnishing. Temperature is, perhaps, the most important consideration. The surface to be varnished should be, preferably, between 70 and 80 degrees and surely not below 60 degrees. Heat is needed to make the varnish brush and flow properly. The varnish itself should be warm too, as nearly the same temperature as the wood as possible. If the varnish has been chilled in transportation or storage, never use it until the temperature has been raised by placing the can in a pail of hot water, about 110 degrees F. is best, or by letting the can stand near, not on, a hot radiator a day or two if possible. If the varnish has been subjected to zero temperatures for days, or even 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 seedy, sandy or specky varnish when it is brushed on to the surface.
¶ Moisture in the air in excess of normal may cause trouble with varnish. Hot, humid days: and cold, misty, muggy days are very hard on varnished surfaces. Keep the windows closed in a room which has been freshly varnished if the weather changes to excessive humidity. Most varnishes are made to perform perfectly under normal humidity. There are varnishes made which will do equally well in very moist atmospheres and they should be secured for use under those conditions.
¶ Ventilation is very important to have because varnish dries by evaporation of the volatile thinners used in it and by taking on oxygen from the air. The air in a room soon becomes loaded with the fumes given off by the varnish and the oxygen in the room is soon exhausted. Therefore the more frequently you can change the air by ventilation of the proper kind the more rapidly the varnish will dry hard. Ventilation should be secured without having drafts blow directly upon the fresh varnish, however, if trouble is to be avoided by having the varnish dry flat or do many other undesirable tricks.
¶ It is a good plan to apply your varnish, in buildings where many mechanics are at work, the last hour or two during the day when there is less likelihood of vibration caused by others walking through the room or building, raising dust or causing it to drop from ceiling or walls.
¶ Storage and Handling of Varnish. Since varnish works, best at a temperature of about 70 degrees it is-well to keep your supply in storage at about that temperature. The top shelf in the shop is often just the right place for it.
¶ All cans in which varnish is kept for any length of time should be full of varnish. Partly filled cans, obviously, have considerable air at the top and that is sufficient to cause a skin to form over the varnish, especially, if the cork is removed often so as to renew the supply of air. It is evident, also, that all cans containing varnish must be kept corked tightly all the time. Varnish which has been allowed to skin over should be strained through silk or fine muslin and placed in new clean cans. A double thickness of cheese cloth, silk or other finer cloth make good strainers.
¶ Getting Clean Work. High quality varnish is absolutely clean when it leaves the factory, and it leaves in clean cans. It is not really difficult to produce varnished surfaces which are completely free from grit, dust, skins and other imperfections, if the finisher will train himself to do many little tasks well. He must be a "crank" about perfection in cleanliness. He may have the job and tools ninety-nine per cent clean and that one per cent dirty will ruin the whole job. For instance, the finisher accustomed to working in buildings doesn't often give a thought to cracks, corners and crevices as places which conceal loose dirt which will be dragged out upon a clean surface by a clean varnish brush when applying the varnish, yet the automobile painter searches out every possible hiding place for grit before he flows on a coat of varnish. Every crack, hole and crevice around hardware and elsewhere is sealed up tight with a small brush and a coating of shellac. If there is any dust in such places, any grit from sandpaper or pumice stone rubbing he makes sure that it stays there by sealing it up with shellac because he cannot completely remove it, can't even see it as a rule.
¶ Before beginning the application of varnish the first step is to see that the surface is clean, not nearly clean but perfectly free from all loose particles, and the final cleaning should be done but a few minutes before the brushing of the varnish begins. A surprising amount of grit can settle on a surface in a quarter of an hour, especially if there are people moving around in the room or if the windows and doors are open. How to clean the surface varies with jobs. After sanding a good brushing with a clean duster brush makes a good start. And for ordinary work a final wiping over with a cloth or chamois akin dampened with benzine, turpentine or benzole will remove the grit. The automobile finisher uses what he calls a "tack rag", a cloth dipped into a mixture of varnish and turpentine and allowed to dry until it is a bit sticky and until none of the varnish would come off on the surface. The varnish is squeezed out of the rag after dipping, of course and before it is allowed to set. Wiping over the surface with the tack rag picks up all loose grit.
¶ With a surface that is known to be perfectly clean the next place to look to for grit which may ruin the job is the brush to be used. It is hopeless to try to produce clean varnishing with a brush which has been used for paint, shellac or any other material than varnish. It is difficult to do clean work with a new varnish brush, so a new brush should be shaken and worked with the fingers until all dust and loose bristles have been worked out. That will take a few minutes time. Then such a brush had best be used a few times for application of varnish under coats, not for finishing coats. Then if it is made perfectly clean after using by washing in at least two pots of turpentine, or a pot of benzine first and a pot of clean turpentine next, it will be in good shape to do a clean job of finishing varnish. Brushes which have been kept in a bath of brush-keeper varnish should be carefully worked free of such varnish by wiping it on the edge of the keeper tank. Then brush out as much more of the varnish as you can on a dry, clean board. Then work it well into the varnish you are going to use, but be dead sure that there is no dried varnish skin clinging to the upper ends of the bristles nor on the metal ferrule sides.
¶ The varnish should now be considered. If good quality varnish which has been sealed up in the original can is used and if it has never been subjected to freezing or zero temperatures it is safe to assume that it is perfectly clean and free from solid, gritty bits of gum or drier. Otherwise, if in doubt strain the varnish into a clean pot or can. And remember that a pot may be clean and shining and still have grit in the side or bottom seams.
¶ Surfaces Fit to Varnish. Before one can reasonably expect success in varnishing the surf ace, old or new, paint, varnish filler or any other should be free from moisture,, both in the surface and on top of it. The varnish defects resulting from varnishing over moisture or sap in green wood are many, blistering being the most common result. Surfaces to be varnished must be free from oil and from grease of every nature, including the greasy film left by human hands and fingers. The surface,, if varnish, paint, filler, etc., should be equally as elastic as the varnish to be applied or a little less elastic, never more elastic than the last coat, if trouble would be avoided. Surfaces composed of varnish, paint, filler, stain, etc., must be bone dry and hard, each and every coat of it and one at a time, before a new coat of varnish is spread on. It is foolish to take a chance on violation of this principle. It is not a good gamble to cut the time of drying short because you never have a chance from the beginning; the result is a certainty, a failure in durability or appearance. Crazing, cracking, flaking, etc., are among the fruits of applying varnish over surfaces which are not hard dry.
¶ Surfaces having considerable gloss should be sandpapered or rubbed with pumice stone and water enough to remove the gloss before applying varnish, enamel or paint.
¶ The secret of success in obtaining smooth, first class work is contained to a great extent in the preparation of the wood, and unless a little care is exercised on the initial stages of the job, the final coat will not show up well. Where a perfectly smooth and level surface is desired the woodwork must be sandpapered down well with No. 00 sandpaper and all traces of dust removed with a hair duster.
¶ Wherever it is possible, and that is in most places, it is a good rule to sprinkle the floor with water or wet sawdust in order to keep down the dust. Beautiful workmanship is often finally marred by floating dust settling on the surface of the work.
¶ To avoid trouble, old surfaces to be varnished should be well washed with water in which has been dissolved a little sal soda or any good washing power. Care must be taken to see that the solution of soap is not strong enoxigh to injure the surface of the varnish. Do not attempt to wash too large a surface at one time as this gives the solution a chance to dry up and thus injure the surface. In washing doors and other upright surfaces lay the soapy water on with a soft brush, starting from the bottom of the surface and working up to the top in order to avoid little streams of water which will trickle down and mark the unwashed surface below. Work the surface well over with the brush, then rinse off all traces of the solution with a liberal supply of warm water which is clean, starting at the top and washing down. After drying the Water with a chamois skin, the surface is ready for sandpapering, dusting and revarnishing.
¶ Where wax has been used on old surfaces it is necessary, before varnishing, to wipe off all traces of wax with a rag soaked in benzole, benzine or turpentine. Unless every trace of wax is removed the new varnish coat will crawl and will not dry. In most cases after cleaning with benzine or other wax solvent liquid it is well to apply a very thin coat of shellac before the varnish coat is applied. The alcohol in the shellac will penetrate any traces of Wax film on the surface and gain anchorage better than varnish. Wax left on a surface by the use of liquid varnish removers must also be removed by wasUng in the same way.
¶ Mixing and Thinning Varnishes. The varnish manufacturer advises that you do not thin varnish in any way, that as it comes in the can, it is ready for the brush. That is good advice and could be literally followed to the advantage of all concerned, if a new can of varnish were opened for every job, was completely used on that job and if the thickness of varnish was suitable for every coat on every job. There are very few occasions, however, which justify the thinning of varnish. Varnish in its original condition should never be thinned for second, third and fourth coats. For the first coat, however, on hard woods like oak, maple and birch, a better job will surely result from thinning the varnish about 25% with pure turpentine. This makes a much better first coat than shellac if it is mixed from the same kind of varnish that is to follow it in subsequent coats. This thin varnish sinks into and fills the wood cells or pores and attaches itself more firmly to the wood than if the first coat were thick enough to bridge over the cells.
¶ In this matter of thinning varnish the furniture finisher has the right idea. He takes a pint of the heavy varnish to be thinned, adds to it a quart of pure turpentine, making1 sure the temperature of both is 70 or 80 degrees F. He mixes this varnish with the turpentine in a most thorough manner and lets it stand over night or longer. Then he uses this thin varnish to reduce the thick varnish of the same, not a different kind. Oil should never be used for thinning varnish. Varnishes which have become thick from improper exposure with the cork out or loose must be thinned and strained in the same way.
¶ It is not wise to mix two or more kinds of varnish together, even if made by the same manufacturer, nor different brands of the same kind of varnish, unless you know each varnish thoroughly well and have acquired skill in this sort of thing. If mixed the varnishes should be warm and should be allowed to stand a day or two after mixing to make sure that you have not formed chemical combinations which have bad reactions, such as livering or separation of some of the gums or liquids. It is much wiser to use varnishes for the purposes for which they are made. If you need varnish for a special purpose, consult the manufacturers and get technical advice which is correct. It will cost nothing and may save you considerable money.
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