We really are back on the cutting edge of woodworking technology this month with the hot glue pot. Now when I was at school, the woodworking shop always had a certain aroma. It was a mixture of pine shavings, sweaty boys and dead animals. The dead animal smell was the hot glue pot. For years I’ve been trying to get people I’ve worked with to accept the idea of the smell of a dead animal in the workshop. I tried doing it in Bideford when we had a wood-burning stove in the centre of our bench shop. On the wood-burning stove was placed a cast-iron double burner glue pot. It was great fun. The outer pot was filled about three-quarters up with water and the inner pot held the glue and the idea was that the top of the wood-burning stove would first get the glue pot up to temperature and then keep it there. Of course this never really happened. In the morning the stove was racing away and the glue pot was cold. So you put it on there and forgot it for half an hour. This was OK if you didn’t need any glue for the first half-hour. But sooner or later the damn thing would reach meltdown. This was when the water from the outer container would boil over and make a loud hissing noise and somebody would dash to the glue pot and move it to a cooler part of the wood-burning stove. Worse than this was the dry meltdown. This was when the glue pot had been left unattended for a few hours and the outer pot has burned totally dry. So without a small boy to tend the hot glue pot everything became a little fraught . All that faffing around with the glue pot seems to have stopped me from using this incredibly good furniture making glue. Until now that is for now I’ve got an electric glue pot. A double boiler glue pot that overcomes all of those problems, well everything but the dead animal . So what’s so special about pearl glue, or hide glue or animal glue, for all these are common names for this type of glue.
This was when the water from the outer container would boil over and make a loud hissing noise and somebody would dash to the glue pot and move it to a cooler part of the wood-burning stove.
This glue is almost the oldest glue known to man. It’s made, as the name suggests, from bits and bobs of animals boiled down to a dark brown sticky substance and sticky it is. For this is an extremely strong glue and in the right situation I would trust its strength in preferance to P. V. A. or Cascamite . It’s gap filling which is useful not that we ever have any gaps and as long as it’s applied properly is very resistant to all the changes of humidity and temperature that a piece of furniture might experience. It is however not especially resistant to damp or moisture or alcohol. Put your piece of high glued piece of furniture in a damp wet barn for a few months and you might find joints being affected but for general use it is a very nice glue to use. It has an awful lot of properties that make it very attractive.
One of them for me is the way it sets up in two stages. You can bring two pieces of wood together with hide glue, hold it in place for a few seconds, then let them go and the joint will hold now the only glue I know that does that is that horrible contact adhesive the sniffers use. Mind you this joint won’t hold under immediate pressure but if the joint was carefully set aside and allowed to cure, that joint would harden nicely overnight. The first stage of this glues drying process is a cooling one, for this is hot glue. It’s best kept at a steady temperature just about blood temperature. It shouldn’t ever boil otherwise the strength of the glue will be impaired. But once that glue chills off from blood temperature to ordinary room temperature it suddenly gets very sticky and very adhesive and very tacky. This is the time your joints should be brought together. It’s possible, using hide glue, to rub joint the two surfaces together without using any clamps. Put a smear of glue along one edge of a board, allow it to approach the stage when it’s starting to chill off, then bring the edge of your second board to it and rub those joints together, very quickly and what was slippery becomes a bit stiffer and a bit stiffer.(be careful what you are rubbing at this point) Once the joint is up leave it alone don’t fiddle, stand the two boards, now jointed, against two sticks leaning against a wall so the air can get to both sides and leave them alone until the following day. I said this was a two stage drying system this second stage takes 8-12 hours and is the process of loosing moistureThen that joint will have been accomplished without the use of expensive sash cramps. (Now there’s an idea).
Mind you this joint won’t hold under immediate pressure but if the joint was carefully set aside and allowed to cure, that joint would harden nicely overnight.
High glue comes in many forms but the most common use by woodworkers is dried pearls or pearl glue. These can be added in small quantities to an existing glue pot, being careful to not get them on the sides of the pot where they will stick but when you start off a fresh new glue pot you have got to cover the pearls in water. Do this first and stir. Then come back after 5 or 10 minutes and add some more water. If you do this every 10 minutes for half-an-hour or so you will probably have added enough water to get your glue started. Just keep the pearls covered or they will swell and absorb water very quickly. You don’t want to add too much water otherwise the glue will start off too thin and runny. You’re next stage is to apply some heat to melt the glue. This is best applied by these modern wondrous thermostatically controlled glue pots. These apply just the right amount of heat all day long, to melt your glue. They take about quarter of an hour or so to get warmed up but once they have reached temperature and your glue has melted all you have to do is attend to the glue rather than attending to the glue pot. Tending to the glue is a process of occasionally adding a little bit of water when the glue is starting to get a bit too thick and heavy. I know this sounds imprecise but you will sense when you have to put the glue on to a surface that it’s getting too thick and when that occurs and it will occur throughout the day as the glue looses moisture through evaporation, add a little bit more water. I said earlier that the woodworking shop smelt of dead animals, there is an aroma to this kind of glue but it’s not an unpleasant one or it shouldn’t be. A nasty smell is the sign of a poorly attended glue pot.
When you start using this glue I would advise that you use it on a small project first. Get the feeling of using it on some solid wood joints for example. What I am going to show you is one of its more interesting uses and that’s in hand hammered veneering. What I’m veneering here is small batch of boxes which are veneered on an MDF ground and we then run Rosewood lines or Ebony lines all the way round the outside corners. Doing these in a veneer press is a constant fiddle because you have to take them in and out of the veneer press four times and you have to trim the job up when the glue has dried which is a fiddy and time consuming job. This lends itself to hand veneering and would be a perfect size to start with. First make your box, then sand it all over so that any trace of glue or rough edges are removed. You can if you wish put a key on the surface with a toothing plane or a bit of broken hacksaw. I do it on some boxes but not on others and it doesn’t seem to make a lot of difference. Next cut out your veneer. In the photographs we are using Ripple Sycamore. Cut them so they are just a shade larger than the surface you are going to be applying the veneer to. Next you are going to need a veneer hammer and a sponge and some water. The veneer hammer as shown here is one I made myself but you can buy them. The essential thing is that it should be a brass strip. Some people use 3 inch brass hinges which have a nice bits of round back but mounted in a wooden block and then fitted to a handle. The essential thing is that it’s a straight surface bearing on to the veneer with a relieved edge if it’s a piece of barr. You don’t want a sharp cutting edge on your veneer hammer. The veneer hammer should have a longish handle. Although you are bearing down on the head of the hammer, the handle is used to pull the veneer hammer in a zig zag across the veneer so you’re squigging out the glue under the hammer.
If something is just not quite down lift it up, peel the corner away, ease a bit more glue in with a small glue brush, wait 10 – 15 – 20 seconds to let the thing cool off then rub it down with the veneer hammer and your excess glue should squeeze out really beautifully.
First apply the glue to the ground. In a small project like this just apply it to the ground not to the veneer. Next take the sponge and just lightly dampen the top surface of the veneer. This will make the veneer curl inwards away from you. Now go back to your ground and just touch the glue surface – is it getting sticky or tacky? Work the bit of glue that is now on your finger between your finger and thumb and sooner or later it will start to get very sticky. This is the time to be putting the veneer down. Now you have got to work quickly. Put the veneer down and start to work the hammer in a zig zag motion bearing down as hard as you can across the veneer. This will squeeze out the excess glue out to the edge of your job. As you are only working in this small area you should be reasonably successful first time but you’ve got five more surfaces to get perfect with. Work over it bearing down making sure you’ve got as much contact as you possibly can then turn the job over and with a scalpel trim off the excess veneer and the squeezed out glue. Do this straight away before the glue hardens and it’s a much easier thing, a much easier process, the glue will just peel away easily. You can if you’re passinonious put it back in the glue pot or if you’re an animal lover you can feed it to the cat. If a corner has not stuck down properly, don’t worry. This is a very flexible and forgiving process. If something is just not quite down lift it up, peel the corner away, ease a bit more glue in with a small glue brush, wait 10 – 15 – 20 seconds to let the thing cool off then rub it down with the veneer hammer and your excess glue should squeeze out really beautifully. If you make a mess just bring a sponge into play and wipe off the messy bits. Be quite controlled about this don’t let anything get in a mess. If you can keep a bowl of warm water around you can keep your hands and your tools all nice and clean. If you do get in a sticky mess and I’ve seen people get in an awfully sticky mess doing this job, go back, clean the tools, think about it and start again. Using this glue is about timing, is about applying the pressure when the temperature is right. If you hammer the glue down too early whilst it is still hot it won’t be sticky at that stage in its drying process. If you hammer it down too late after the glue has chilled then you will have a terrible job getting the excess glue out from under the veneer. A little bit of glue, a little bit of pressure and a nicely made joint is the maxim for all glue ups but it’s especially useful in this context. Try it – high glue is one of those glues that will enable you to do all kinds of work without cramps, without enormous veneer presses, without a whole bundle of equipment that you don’t need, just learn how to use this lovely glue and you’ll find yourself sticking all sorts of things with it.
