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I've decided to switch to hot hide glue for neck and bridge attachment.
Can you tell me what strength of hide glue you prefer for these particular procedures?
Also how thick (water/granule ratio?) do you usually make it?

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Formerly know as Mandodiddle.

have used both 192 and 215
they are both plenty strong enough.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

I like the 192 stuff from LMI. Not sure what the exact water proportion is. I err on the low side to start, and then add more water until it's just right. Put out a drop of glue and let it cool, and then press on it with the back of your thumb nail to feel how firm the gel is. If it springs back to shape even with a fair amount of pressure, it's too dry. If it squashes with minimal pressure, it's too wet.

I just use 192 gram strength, and it works great. I normally use a 1.6 water to 1.0 dry glue ratio, measured by weight, not by volume. If I need it to be runnier than that, I add more water. I rarely need it to be thicker than 1.6 to 1.0.

Leaving aside the question of strength for a moment, the higher gram strength glues gel much faster than the lower gram strength glues. So, whatever gains in strength come from using a higher gram strength glue, you have to move faster during joint assembly. Not good or bad; just something to be aware of.

I suspect John may have meant 315g, rather than 215g. I couldn’t find any 315 when I was stocking the shelf, I use 260g on bridges, 192g for everything else.


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315 for bridges, vacuum clamped. 192 clear for everything else.

1.9:1 water/glue by weight.

meant 251 strength

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

I have been using 192 for just about everything. Recently got some 315 from a discussion on Torrified tops and bridges as per Woody's suggestion to use 315.

For a dovetail neck joint I would think 192 would be best.

I use 192 for everything except bridges on torrefied spruce, for that application I use 315.

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Steve Smith
"Music is what feelings sound like"

192 for neck sets, bridges, headstock repairs and anywhere else that HHG makes sense.

192 is plenty strong enough for bridges that are properly fitted and the patch is properly prepared and the rest of the box is in order meaning no loose braces or bridge plate "tenting" that will lead to the bridge lifting again.

I'll add that it's more important than what gram strength that one uses for one to have the chops, knowledge, dry runs (the verb not the malady...) and an understanding of HHG to meet the short open time requirements. If you cannot have things in place and snugged down fast enough other glues may be a better choice for you.

Me thinks that the whole point of HHG was the original KISS thing, keep it simple stupid..... We tend to make this overly complex when we discuss HHG here but the open time requirements is real, important and will bite ya if you ignore it.

So what kind of open times do folks feel like they are working with?

_________________
Formerly know as Mandodiddle.

Trick question! Personally, I try really hard to not bump up against whatever the pre-gel time limit is. I plan out gluing operations that allow me to spread the glue and get the parts clamped in less than half a minute. If it will take longer than that (which for me tends to only be the case for gluing plates to rims), I preheat the parts and add a smidge of urea to the glue, just to avoid the dreaded gelling. For everything else, if you can’t plan it out to get it done in less than half a minute, there is some dawdling going on. Just my opinion.

I’ve never had a bridge pop off in service using 192. When I was first starting to use HHG on my own builds I lost one due to poor process - not getting the clamps on in time. Now I have no problem getting the budge on and clamped in 10-15 seconds. I preheat parts with a hair dryer for a few seconds and work in a warm room.

Caveat here is I don’t deal with much torrefied wood - if you search you’ll see posts from Woodie outlining her process for using higher strength glue for these.

One (of the many) things I like about HHG for bridges is that failures tend to manifest quickly when stress is applied to the joint. So if you screwed up you will know about it shortly after installing the strings

That means if something goes wrong you have the opportunity to fix your mistake (easily and quickly, thanks to the forgiving nature of HHG) before the instrument leaves the shop.

192 for everything. 315 for repairs.

We shoot for ten seconds or less with 192, 15 seconds is fine too we just always are trying to do better than last time.

We have a unique way of doing bridges where we preposition the clamps in the exactly location that they need to be so that all I have to do is slap the bridge down in a pocket made of masking tape and snug the clamp(s). I can usually have my bridge clamp in place and snugged in only several seconds with this technique.

We've never had any need to use any other gram strength HHG than 192, no bridge lifts (except for the fish glue bridges I speak of here when it comes up).

It should be mentioned even though all I use is 192 that other gram strengths have a different open time, the more the gram strength the less the workable open time. One of our attractions to 192 only is we don't want any less open time as it is 15 seconds is fast for some repairs anyway.

The higher the gram strength the less viscosity you have. Hot Hide Glue 192 is plenty strong and you will have the most open time with this.
I also suggest to warm the area to gain as much open time as you can. When I tried higher gram strengths I have a few failures due to the clamping issues.
They are easy to reglue but I now use almost all 192 and 215

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

I just jointed two torrified red spruce tops with 315. I use wedges to clamp the two halves together and what I found was that there was not enough time to get it clamped before it gelled up. But once it was in clamps and I hit it with a heat gun the joint closes up and after sanding them the joint is totally invisible.

I know a lot of luthiers just do simple rub joints but I tried that last week on these tops and there was a visible line so I sawed it through and redid it with clamps.

For those who use 315, or any others for that matter, what is your ratios when mixing? I have 192 from LMI and they recommend 1.8 water to 1 glue by weight so that is what I use. For the 315 I used 1:2 glue:water.

If you build using the peones the 315 is fantastic as you just hold it there for a couple seconds and it's stuck.

I mix 315 just like any other HHG, I don't measure anything. I put granules in a 1 oz bottle and then add distilled water till it just covers the top.

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Steve Smith
"Music is what feelings sound like"

192 for everything, seems to work. I mix like Steve, enough water to just cover the granules in the bottle.

For braces and bridges I lay a heating blanket on the bench and run it about 160-200 with a surface thermometer. The parts sit on it until ready to glue. I heat the recipient surface with a hair dryer.

With braces I clean up squeeze out with tapered wood sticks followed by a toothbrush and paper towels with hot water from the glue pot. Hitting the area with a heat gun afterwards to dry the wood hopefully reactivates any glue that may have gelled prematurely.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Like Terence, I use 192 for everything. They all break wood!

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Jim Watts
http://jameswattsguitars.com

The beauty of HHG is it's simplicity... Please keep that in mind.

Given the same amount of water per weight of glue, I'd agree, but it's easy to add hot (150-160 deg F) distilled water to adjust viscocity, or simply heat the glue to a higher temperature as is done when better penetration is needed. Sure - the strength of the glue is compromised if that glue is reheated and then used again, but a quick boost to 185 degrees for 192g gives a 90 degree cushion on gel temp versus the usual 50 degree cushion for 145 degree glue... with a little thinning, that gets 192 gram strength glue much deeper into a neck break.

All of the common gram strengths are technically strong enough in a perfect joint, but bridge joints on repairs and even new guitars are seldom perfect, so the better the gap filling capability and tolerance to thicker glue lines, the better. This is why we used 315g for bridges, as we saw plenty of 192 and 251 glued bridges on previously repaired or custom built guitars (NOT ours) part company after a few months or years. 315 does not make sense for any application where the joint can be perfected AND where the clamping is perfect, but for the average bridge joint - under constant loading and operating near strength limits - it is cheap insurance. Preheating the bridge handles imperfect technique on glue-up by providing a reservoir of additional heat energy to remelt the glue on the bridge patch as the joint is closed. A plate warmer does a nice job of bringing the bridge up to about 165 degrees... heat for 10 minutes, which is enough to get a consistent temperature, but not long enough to cause resin bleeding on rosewoods and some ebonies.

315 gels at about 130-135 degrees, so without a secondary source of heat (i.e., the thermal mass of the bridge at 160-165 deg), open time is measured in tens of seconds (allowable cooling during assembly = glue temp - gel temp = 145 deg - 135 deg = 10 deg!!!), which is too little time to close and clamp the joint. Therefore, 315 requires a method to add supplemental heat which 192g (95 deg gel) and 251g (115 deg gel) usually avoid through good technique and a bigger temperature range between glue temp at application and gel temp.

192g for everything else.

Do you guys always use distilled water when mixing HHG?

I am sure that many people do, but I just use tap water. Seems to work fine.

I just use tap water too.

_________________
Jim Watts
http://jameswattsguitars.com