Mixing, Brushing, & Wiping Paste Fillers

¶ Mix and color the filler, if it is to be colored rather than used in the natural color, as indicated in the preceding pages of this chapter.

¶ Thin the heavy paste with benzine until it brushes freely and yet is fairly thick. Tempering the mixture to have it just right is very important. Try out the mixture on some out-of-the-way place or on a sample of the wood you are going to finish. The filler should be used thinner for walnut, gum and similar woods than for oak, chestnut, ash, elm etc.,the latter woods have larger pores or cells to be filled.

¶ Coat the surface freely with the filler using a stiff brush to rub the filler well into the wood. Brush the filler on with the grain, lengthwise of the boards, but lay it off to finish brushing across the wood grain. Wood pores are filled with air-which forms a cushion. The filler will not sink in to the bottom of the cells unless thoroughly brushed. When the filler mixture is just right it will fill the wood pores and set up with a dead flat surface in from two to five minutes, depending upon the amount of ventilation and the temperature of the room.

¶ If the filler settles quickly into the pores of the wood, leaving the liquid on top, too much benzine has been used.

¶ Filler used by the house painter is usually tempered to save time. It contains very little oil and it sets flat ready for wiping in from two to five minutes, as has been said. It sets so hard in half an hour, usually, that it cannot be wiped off. The furniture finisher takes more time. He likes to temper the filler so it sets ready for wiping to begin in about 15 to 20 minutes, and yet so it can be wiped any time up to an hour or two after brushing. It will dry hard in twenty-four hours and will thoroughly mature and harden in forty-eight hours.

¶ When the filler has been brushed on to a small area of surface and has set flat it is ready to wipe. A handful of excelsior or burlap may be used. The furniture finisher prefers to use a large wad of curled hair, the horse hair stuffing used in the cushions of upholstery. Sea moss (grass) is preferred by some, as doing a quicker, cleaner job of it. It is pretty hard to beat good excelsior, however. The wiping must be done across the grain of the wood and in such a way as will not lift the filler out of the cells but will cut it off sharp and level with the top of the wood fibres. The object of wiping is to remove all filler which is not lodged in the wood cells. If any is allowed to remain on the surface of the wood it will cloud the finish and give a muddy appearance. After wiping over a small area with the excelsior or other coarse material to remove most of the filler wipe over it again with clean cotton rags, but use no rags which leave lint. The cleaner the job of wiping the less sandpapering you will have to do when the filler is dry. Do not wait to begin wiping until the whole area coated in has turned flat; begin wiping the first filler brushed on as soon as flat spots appear, being careful to rub the filler into the wood cells as you wipe. In other words note carefully how the filler is coming off before you wipe too much.

¶ If your filler has been mixed and tempered correctly it will roll up under the excelsior wad and come off easily. If it seems tough and hard to remove you have waited too long before wiping. You may have to wash the surface with benzine, let it dry and start over again to brush on the filler and try a second time to wipe it at just the right time.

¶ If the filler lifts out of the pores when wiping after it has set flat, too little binder has been used. Add ½ pint of japan drier to 1 gallon of filler.

¶ When a filler has too much oil in it it will not roll up as it should, like putty, when wiping. It will be sticky and will pull out of the wood grain and cracks.

¶ When the filler after being mixed correctly sets too rapidly and becomes dry before wiping, stop part of the ventilation and coat in smaller areas of surface so you can get back soon enough to wipe before the set is too dry. It may also be necessary to add a few drops of linseed oil to the filler to slow up the setting. Be very careful, however, not to use too much oil. A surprisingly small amount of oil is needed and too little is better than too much. Oil makes the filler tough and prevents it from wiping off clean and level.

¶ Filler which is mixed too stiff, not enough benzine, will take an excess of labor to brush it on and it will roll out of the cells of the wood while wiping.

¶ When for any reason filler sets so hard that you cannot wipe it, brush on some benzine, let it set again and wipe when just right, or wash off the filler first coat and take a fresh start.

¶ Don't coat a large area of any surface with filler until you try a small area to test out the brushing, wiping and filling qualities of the mixture. By following that suggestion you will save yourself much time and labor. As a matter of fact many finishers work much harder on filling jobs than they need to if they would only use their heads more and their muscles less. Learn how to temper the filler just right by experimenting and then it will wipe off easily, fill the cells well and do a clean job. If filler is permitted to dry hard before being wiped a great deal of labor is needed to remove it with scrapers and sandpaper.

¶ An examination of the filler after it has been wiped and is dry will show whether the mixture was tempered correctly and properly brushed and wiped. Pinholes in the filler result from using too thin a mixture or from too little brushing. When the pores are not well filled, the filler was mixed too stiff, not enough benzine in it, or it was wiped off too soon. When the grain figure is clouded and muddy in appearance, the wiping was not done well enough to clean up thoroughly or the wiping was delayed too long.

¶ While brushing on paste filler it should be stirred every three or four minutes. If not, the filler used off the top of the pot will contain too much oil and what is used from the bottom later will contain too little oil. The pigment settles rapidly unless cornstarch or asbestine have been added to it.

¶ If a filler containing too much oil is used on woods having an excess of oil naturally, like rosewood and cypress the excess of oil will ruin the varnish finish. The same is true when the surface has been shellaced before filling. And when filler containing too little oil or japan is used on mahogany, walnut, gum, etc,, the filler will turn gray in the pores and so a clouded finish will result, giving somewhat the same appearance as the use of white shellac on dark stained finishes, instead of orange shellac.

¶ Narrow mouldings, edges of cabinets, table tops and similar surfaces are more difficult to cover with a uniform thickness of filler than flat surfaces. It is necessary sometimes to put two coats on these. Let the first coat set flat before brushing on the second and then wipe both coats when the second is flat. Delicate carvings are never filled with paste filler. One or several coats of shellac are best, because the filler fills up the depressions and rounds off the sharp edges too much.

¶ When filling and staining in one coat it is best to add about 20% benzole to the filler in place of some of the benzine. It will then penetrate and color the surface more deeply.

¶ Where oil stains are used it is desirable to precede the filling with a very thin wash coat of shellac, as there is some danger that the filler with its linseed oil content might soften and wipe up the stain. Thus a muddy, cloudy color effect will result.

¶ Where it is necessary to use paste filler on large surfaces, as on floors, wall panels, etc., reduce only enough of the thick paste with benzine for a day's work. When the filler which has been finally thinned is allowed to stand over night the pigment not only settles to the bottom but some of the solvents evaporate and a thick mixture which will not work as it did the first day results. If you add more benzine by guess to take the place of that which has departed you cut the oil too much and the filler may dry out powdery. It is really better to add a little more linseed oil, but too much oil will make the filler tough and it will then require more labor to wipe it off clean.

¶ Paste filler should not be mixed too far in advance of your needs. It is better two days after mixing and up to about two weeks after mixing than it was the first day, if kept covered up so the volatile liquids cannot get away.

¶ After being wiped clean paste filler should dry not less than 12 hours and a longer time is much better. Some finishers put on a second and thinner coat of filler, wipe and let it dry. This is to avoid all risk of having the varnish coats sink into unfilled cells and dry with a pitted effect.

¶ When the filler is bone dry, sandpaper the surface with No. ½ paper and wipe the surface up clean with a cloth dampened with benzine. That clears up the wood grain considerably, making a finer finish. Of course, if the wiping of the filler has not been well done it will be necessary to sandpaper more. Use, then, No. 1 for the first time over and finish with No. ½ or finer paper.

Next Page: Liquid Wood Fillers.