Tuesday, November 22, 2011

Old and New Protein Glue

I have had the cast iron glue pot cooking near my bench for over40 years. Every day I turn it on first thing when I open up the shop and every day I turn it off when I turn off the lights. There has been a note inside the front door which asks: "Glue Pot Off?" for as long as I remember. More than once in my career I have woken up at 2am and returned to the shop to see if I forgot to turn it off. About 30% of the time it was on; the rest of the time I just mumbled something and returned to bed.

For the past two decades I have also been developing and using a liquid form of this glue, Old Brown Glue. The demand for this glue has grown tremendously through word of mouth and the fact that it simply works great. It has a long open time, bonds well, penetrates better than hot glue and is much easier to clean up.

Currently I am repairing a nice set of English Regency mahogany chairs. Doing the gluing on a large set of chairs at one time requires that I use a glue with a fairly long open time, so I use the OBG. In some cases there are small fragments of wood which are broken away from the joint. For that I use the hot glue pot, since the bond is almost immediate.

So the glue pot sits next to the OBG system in the center of the shop, just a few feet from my bench and the wall of clamps. For the OBG I use a simple tub of hot tap water, which I change from time to time as it cools. The bottle is kept in the water so it is liquid. On top of the water I float a small plastic cup which holds the brush and glue, ready to use. I can take that small cup to the bench, make my repair and quickly return it to the water so it stays ready. In addition to keeping the glue liquid, I can use the tub of water to wash my hands or wet a paper towel to clean up the joint. Very practical and easy.

And I do not have to wake up at 2am and worry.

This project also serves to demonstrate more vector clamping methods. As the regency chair form is fairly common, I always have blocks ready for clamping in place. First I just tape the block where I want it, so I do not have to have three hands. Then I put the glue on the joint and apply the clamp. Normally, if the blocks are made correctly, only one clamp is needed to close the joint. The second clamp serves to hold the block in position.

Looking closely at the photos, I need to make two comments: First, the wine bottles are full of water based stains, not what you think. Second, there is a belt sander on the floor...one of the few nasty tools I have used and not something I am proud of. However, have you ever tried to hand sand sharkskin? It has the density of teeth!


Anonymous said...

After using mostly yellow glue since the early 90's I ordered a bottle of your Old Brown Glue. I want to transition to reversibles. In this blog you mention using the water for clean up. I'm assuming this is right after clamp up and before the glue sets up. And after the glue sets up, you just scrape it?

W. Patrick Edwards said...

With the hot glue it sets so hard and fast that I need to use scrapers, chisels and other tools to remove the excess. That often damages the finish.

Not so with the OBG. OBG takes longer to set, since it relies on loss of moisture to cure. Thus, inside the joint, where pressure drives the moisture into the wood, it sets nice and hard and fairly quickly.

However, the excess glue which sits on the surface dries more slowly, depending on the relative humidity and temperature in the workshop. Therefore, it remains rather flexible for some time and eventually hardens.

That means that, when I glue up a project, I use simple damp paper towels to remove most of the visible glue on the surface, at the time of clamping. Then, the next day, when I remove the clamps, I use cold water and a sponge to wash away the residue, cleaning up with dry paper towels. This method actually protects the finish and no harm is done.