Gluing Bridges with Hot Hide Glue

[Nicholas Peshman]

So I am ramping up for my first acoustic build and am planning on using hot hide glue for a few parts mainly for the bracing and am playing around with it now of some side things (like wooden hold fasts) to get get a feel for its use and application. In some you tube and build video (I believe Robbie is one) they say that with Hot Hide glue doesn't really require clamping that its "self-clamping" of course if the joint is proper and its held for several seconds. What I have used hot hid glue for thus far certainly backs that up after about 30s its going to take a bit to get the parts apart again. So okay I watched a few videos of people applying bridges with hot hide glue, but so far everyone that I have seen has added clamps. I am pretty certain that by the time the last clamp goes on that glue is or is nearly set and I would have thought that this relatively tricky part of the build would use this aspect of the glue more frequently. So what say all you more experienced folk? I don't think clamps would hurt anything as long as they were applied quickly enough. With that said as long as I block in the bridge so it can't inadvertently move I would think that those precious seconds would be better spent applying the pressure by hand. If it matters I was using 315g glue in my playing around with it.

Nick

[Stephen Foss]

Nick,

Let me gather my photos and I'll show you how I'm doing it. Yes, I use clamps; I've got it so it takes about 10 seconds between applying glue and getting it clamped.

Steve

[Stephen Foss]

Nick,

Here's a few photos. I've since stopped using the LMII bridge clamp (I found it unnecessary).

The clamp. I double stick tape the 'bridge-patch' shaped caul under the bridge patch, then place a sponge inside the guitar to hold up the inner part of the clamp. I then stick the smaller piece of plywood into the guitar with the bolt sticking up through the sound hole. The padding on the top piece keeps the finish from being dinged, while the other end of the clamp sits on top of the fretboard. The two little dowels will become apparent in later photos.

The two outside bridge pin holes have "locating" dowels. You can see one of the corresponding holes in the top. These get drilled out the next day. The two smaller dowels in pin holes 2 and 5 make a 'handle" for the bridge. These pins are sanded to be too small to stick in the bridge pin holes, but, when squeezed, it's easy to manipulate the bridge and then spin them to easily pull them out.

Layed out and ready for HH glue. I have since stopped using the LMII bridge clamp thingy (too fiddly). 

The clamp knob is at this point loose. Using the bridge 'handle', apply plenty of HH glue, set the bridge onto the locating holes, hold it in place with one hand, spin out the handle-dowels, then slide the clamp over the center of the bridge and tighten the knob. This literally takes 10 seconds from applying glue to tightening the knob. To clamp the wings, I use cam clamps between the bottom of the guitar and the bridge (thanks Paco Chorobo!); they don't need to be too tight and the caul underneath provides plenty of strength. 

I have since seen someone use this method, but with a camp clamp in place of the plywood clamp that I use. I also have a vacuum clamp (LMII), but the HH glue squeeze-out is much easier to clean up without the vacuum clamp in the way. Since HH glue sets/cures by evaporation AND a drop in temperature, I'm not sure how the vacuum clamp might affect the evaporation rate. Maybe the engineers in the group will chime in. This is so quick and easy though.

I'm using  Higgins 192 gram strength glue. I immediately clean up the squeeze-out with a tapered stick and a cotton ball with warm water. I leave it clamped up overnight.

I hope this helps,

Steve

[Nicholas Peshman]

Thats a great method. Best I have seen yet! Thanks for sharing that Stephen. But is there any structural integrety being lost if no clamp is being used with Hot Hide Glue?

[Steve Johnson]

For my first build, a flamenco, I took some tips from a YouTube video by Michael Thames.  He uses clamps ( so did I )  but he also "primed" the bridge area on the top before he sticks the bridge.   

Priming the top most likely saved me because I hurried too much when I spread HHG to the bridge, (wanting to keep it hot )  then realized after clamping that I probably spread it way too thin.  

I anticipated the bridge popping off when I first strung it up, but it's still holding after 6 months of heavy handed flamenco playing.  (phew)

Here's the video link:    https://www.youtube.com/watch?v=fh-On-44yT0

Hope this is helpful! 

Steve

[Stephen Foss]

Nick,

I don't know about structural integrity that might be lost by not using a clamp because I've never HH glued w/o clamps. So far (knock wood), my bridges have stayed put. If you find/figure out what effect a rub-joint has on a bridge, please share. There was a re-printed article in a recent GAL magazine about Eugene Clark. He apparently used a rub-join for gluing the fan braces onto his classicals. I reckon it works fine on a bridge, too. Since I cut the saddle slot prior to gluing on the bridge, it needs to be in perfect alignment for the scale length, thus the locating pins. The pins made rubbing the bridge difficult. 

I'll suggest that you go over to the Old Brown Glue website and watch some of Patrick Edwards videos on HH glue. As a trial, I've glued both a top and a back on (in a go-bar deck) using OBG. They are still holding firm after 6 months as a strung-up guitar. To warm the lengthy kerfing prior to applying OBG, I painted warm water from the glue pot onto the kerfing, then applied the OBG. Even with the longer open time of OBG, I didn't dilly-dally (technical term) getting the go-bars on.

I started using HH glue merely to find out for myself what it's like. And so far I like it. It wouldn't work for Robbie's week-long class because of the curing time, but I don't have that constraint. Besides titebond is a fine glue, also.

Steve