Technical Articles:
Hot Glue Veneering

By Bo Riley

Hot glue veneering and French polishing are frequent Spinet topics on our 12-1:00 p.m. question hotline. I have just completed our most recent in-house English Bentside Spinet after Baker Harris and would like to share with you, in the vernacular, some hints and observations that might be helpful.

Hot glue is nothing to fear. There are many advantages and few disadvantages of this medium. Most significant is the fact that any mistakes arising from one's technique can be fixed, reworked or replaced with surprising ease.

Preparing the glue is straight forward. Start with 8 oz (a yogurt cup) of dried glue in your glue pot, and add to it 16 oz of cold water, stirring well. Let sit until the mixture swells to resemble a root beer snow cone (dark granular Italian ice is the European equivalent). Cover and plug in the glue pot. Wait about one hour until the mixture is well heated. 140 degrees (F) feels quite hot but is not painful to the touch. A glue pot will maintain this temperature well. The ideal consistency is that of Vermont real maple syrup. If the glue is more like Log Cabin or Aunt Jemima it is too thick and should be thinned by adding hot water 1/8 cup at a time. You may work all day with the pot plugged in. Just remember to keep it covered and to maintain the correct consistency. What you don't use in a day may be covered with plastic and refrigerated. I usually make a new batch after 7-10 days, but up to 14 days should be fine.

A few personal axioms may be helpful:

1. Use a real plug-in hot glue pot. It keeps the glue at a constant, safe, fuss-free 140 degrees (F);
2. Always prepare surfaces to be veneered by brushing on hot glue mixed with 50% hot water. Then scuff with sandpaper (120 grit) when dry;
3. Keep the pot covered with the brush in the pot.

The veneering of the inner case rim is one of the very first operations. The only significant in-house deviation from the kit instructions for this procedure is that we glue to a separate piece of basswood 40+" long the veneer that would span from the left front where it meets the spine past the nameboard to the right front where it touches the bentside. We install stringing, flatten the veneer, and sand the piece. It is then cut on the table saw so the veneer is attached to the basswood as a 1/16" thick 40+" long off-cut. This allows a quick seamless piece that can be glued on after the case is assembled. For this operation one only needs flat, straight stock and some table saw skills. It is not necessary to apply this method to the remaining case parts since the spine and tail are straight and seamless, and the direction of the bentside curve lends itself easily to the traditional method.

Upon completion of the case assembly, the large walnut panels are the next to be veneered. At this point I brush with thinned glue all of the surfaces that are left to be veneered. After the glue has dried place an oversized piece of walnut veneer in the correct location and trace lightly with a pencil the correct location of the walnut. Apply hot glue to the marked surface quickly and well overlapping the lines. Put the veneer in place and brush glue on top of the veneer. Yes. on top! This acts as a much needed lubricant, equalizes moisture content for both sides of the veneer which reduces cracking, buckling and curling, and fills and seals the grain which makes subsequent finishing easier. Quickly rub the piece with the veneer hammer first with the grain then diagonally in all directions working from the center outward. If the hammer starts to drag too much you may either use more glue, or if the pot is out of reach, saliva does very well. The entire process takes about 5 minutes for each panel. Wait no more than 30-60 minutes before trimming the excess walnut from the panel. It should peel off like stiff leather. To wait too long is to find out how tough hot glue really is.

Some helpful hints:

1. Keep the veneer hammer warm;
2. Always keep warm water available as many uses will arise;
3. Be sure stringing joints are tight from top to bottom. Unlike carpenter's joints, stringing joints need to be reduced to the level of the surrounding veneer. If the point of contact is not tight all the way to the bottom, an ever widening gap will appear as the stringing is made flush with the veneer;
4. Stringing can be held in place by pins inserted beside the stringing bent downward upon the stringing;
5. Large pieces of veneer may be heated with an iron prior to gluing;
6. Use an old dull chisel to scrape warm glue away.