Official Luthiers Forum!

Thanks Woodie, useful information as always!

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Steve Smith
"Music is what feelings sound like"

For 315 gram strength glue sources:

We used both standard 315g and high clarity 315g at Greenridge, with no difference in performance or use versus standard HHG other than a lighter color glue line and less dead horse smell to the glue pot at the end of the workday. High clarity hide glue is billed as being more refined (made from animals coerced into cotillion?), but it seems as though pig skins are the primary ingredient. Given bridge work does not tend to produce visible glue lines, either standard or high clarity should be fine for the job.

Tools for Working Wood in Brooklyn, NY still carries 192g high clarity, and sells standard 315g glue.

https://toolsforworkingwood.com/store/item/MS-HIDEGL.XX

I suggest a piano repair supply house as a source for high clarity hide glues - 192g, 251g, and 315g are all used in piano casework, so are usually carried in stock. The supply house we previously ordered from has disappeared over the period of the pandemic, but Ragland - which has an Ebay store - sells 1, 3, and 5 lb quantities at a reasonable price (although the shipping cost is irksome).

https://www.ebay.com/itm/292410333207?h ... SwWMhaXUh3

As always, a direct order to Milligan and Higgins - the source of nearly all HHG in the North American market - will net a per pound cost well below retail, but the minimum order is in the 50 lb range.

Mr. Bond's comment on Titebond is well taken. If done with a very thin, well-made glue line, a Titebond joint should show minimal cold creep and less chance of a finish de-lamination where a net-shape bridge patch is used. For those that use that glue, it appears to do a good job with meticulous prep and usage (we saw enough guitars built with Titebond and giving trouble-free service to recognize that builder skill in making and closing joints went a long way towards mitigating potential issues with that glue).

As a repair shop, Greenridge avoided Titebond and other AR and PVA glues for most work and especially highly stressed joints out of a concern for what we saw as a history of observed issues with both cold and hot creep seen in instruments built or repaired with thermoplastic resin-based glues. After seeing too many of those tell-tale separations of finish in front of net-shape bridge patches on post-mid 1960's Martins, older Olsens, and a range of other instruments in for repair work, we avoided the issue entirely by using higher gram strength HHG, accepting the additional 315g HHG 'overhead' of increased glue/gear cost and labor as the price paid for sleeping a bit easier.

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For the times they are a changin'

- Bob Dylan

How much faster does the the 315 gel? I simply cannot work fast. I have tried heating parts too but I am just not quick enough. I know people say practice practice practice. I tried. Just call it a disability if you must . I found that adding salt to 192 gives me enough time to do everything including bridges. So far in 4 years and probably 100 guitars (including repairs) no issues with strength.

I would also like to mention that a bridge that is fitted well, slotted, with the ball ends under the bridge plate does not have as much stress on it as most think. I tried finding this post on another forum but failed to do so. None the less a guy was experimenting with this idea and built a model, a solid top model, where he didn't glue the bridge down at all and it held there on its own under string tension. Of course being a solid top it doesn't have the same dynamics but still it was interesting.

The 315g I got from Tools for Working Wood is made by Behlens

_________________
Steve Smith
"Music is what feelings sound like"

I've got mine from this place. Lots of different grades, and high and regular clarity. You only need to buy a pound.

https://bjornhideglue.com/shop-hide-glue/

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Why be normal?

Pre-warming the bridge to 150 deg F or so increases the open time of 315g HHG dramatically...we often found ourselves waiting up to 10 minutes after closing the joint and clamp-up before we saw the squeeze-out gel to the point we could begin cleanup.

You'll find that Behlens (a sub-brand of Mohawk Finishes), Brooklyn Tool and Craft Company (BTCC, as sold by Woodcraft, TFWW, etc.), J.E. Moser, StewMac, Bjorn, and other repackagers buy in bulk and make their margins by breaking out those 50 lb drums and bags of granulated glues into 1, 3, 5, and 8 lb poly bags and labeling for resale. Manufacturer of related gelatin-derived products is old-line manufacturing, so there is Milligan and Higgins in the US, Tanex in CZ, and likely a few other makers that do not market directly to luthiers. Some luthiers here in the Americas prefer the Tanex Topaz I (250g), Topaz II (200g), and Topaz Special (300g) glues, and pay the extra cost associated with import, but after a brief flirtation with Tanex products in the 2009-2012 timeframe, Greenridge found that the M&H products satisfied our needs.

_________________
For the times they are a changin'

- Bob Dylan

Oh wow ok. That is a considerable amount of time then. I was hitting it with a heat gun so perhaps not getting it warm enough. How do you heat the bridge up and do you have some way of measuring the temperature?

EDIT: Also I assume you wet both surfaces with the HHG right?

So, cleaned and re-rabbited the bridge, freshly scraped everything, heated the parts to 145F and glued with freshly mixed 315g HHG. Plenty of working time with everything warm. Scraping to glueup done was 5 min max.

I'll take it out of the clamps tomorrow afternoon. Hope it works

_________________
Steve Smith
"Music is what feelings sound like"

Are you guys using a microwave to heat the bridge? Checking temperature with an Hand-held Infrared Laser Thermometer?

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I have used a microwave in the past. In this case I heated it with a heat lamp. Checked the surface temp with an IR thermometer.

_________________
Steve Smith
"Music is what feelings sound like"

I'm confused about the 315 gram strength glue, if I'm pulling fibers off a glue joint with a 192 gram strength glue, i.e. failing the wood, what difference does 315 vs 192 gram strength make?
Thanks

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Jim Watts
http://jameswattsguitars.com

while gram strength is part of it the higher the gram strength the shorter the working time. I have used 192 for 20 yrs to glue bridges and neck , there are a number of articles , one I had used was from a woodworking forum stating gram strength was the amount of working time witch is partly true.
i have used heavier gram strengths but went back to the 192 and 215. In this thread the main reason of the joint failure is that the bridge appears to have been clamped on the finish , this allows a gap and this I think was the main reason of failure. Hot Hide glue is not a good gap filling glue. Also on Torrified tops I use 24 hr clamp time as the wood doesn't absorb water like raw wood . I think there is a lot of good info here and I know I learned a few things. Best to all.

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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

There is for sure good information here, I'm just not sure I understand the why I should use 315 instead of 192. It must be a torrefied top thing.

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Jim Watts
http://jameswattsguitars.com

John - Apparently the photo is confusing - the bridge was NOT clamped on the finish so that did not cause the failure. There is a rabbit on the edge of the bridge that overlaps the finish (french polish). The joint is wood to wood. I've done a lot of bridges this way with no failures.

Per Brooklyn Tool and Craft: "The 315-gram strength is considered optimal for lutherie work and small repairs. It is the strongest of the three BT&C glues with the shortest open time". FYI - the other two glues are 251g and 192g hide glue.

Then there are other articles that say there is no difference in the strength of the different gram weight hide glues and it's just the time to gel that changes.

It's confusing.

Jim, I've always used 192g in the past for bridges with no issues. Torrefied spruce works differently and that is what we are looking at here.

_________________
Steve Smith
"Music is what feelings sound like"

ok it is hard to see in the pic I know your clamp time was shorter. Try the 24 hr clamp and snug not over tight

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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

Thanks for the info Woodie. I generally use Behlen's repackaged HHG at 192g strength. Does anyone happen to know whether this is considered a regular vs high clarity grade? It's not too pungent but if there's a 192 available that smells less like a tannery I'll happily switch to that instead.

Maybe none, Mr. Watts. But for highly-torrified top wood that has already shed a bridge or two, it appears to be the difference-maker for keeping things together. For repair shops like Greenridge that live and die on reputation, it is additional insurance against warranty work walking back in the door.

On wood fibers as an indicator of joint strength, I would want to see something very close to 100 percent wood fiber coverage on a failure test to be comfortable that I had a successful glue joint. Less than that suggests either cohesive failure (failure internal to the glue line...rare in well-made joints) or adhesive failure between glue and top or glue and bridge.

On regular 192g and 315g HHG: I don't find the odor to be objectionable in most cases, but I bought a pound of 192g after leaving Greenridge that stank of a tannery (if you've ever lived near one, the stench is memorable)... I talked Mr. Stock out of 5 pounds of his stuff, and will buy high clarity when I have to restock. While standard glue is earthy-smelling, high clarity tends to be near odorless even when reheated or left in the pot overnight (a bad idea).

By the way, consider storing both shellac flakes/buttons and flake or granulated hide glue in 1 quart or 1 gallon paint cans...dark, durable, airtight, and cheaper than Tupperware in this period of skyrocketing inflation. 5 lbs of granulated glue or shellac flakes will fit comfortably in a gallon can, while a quart can will hold at least a pound of dry material.

_________________
For the times they are a changin'

- Bob Dylan

Wanted to stress that uber good fitting of any bridge is always desirable. Regardless of if you clear finish to the perimeter or something slightly less consider that any flaw in your fitting will be exploited by the harsh environment of an acoustic guitar bridge. From string tension over forever.... to RH swings with dimensionally unstable, newer unseasoned top wood dancing below you it's not fun being a bridge on an acoustic guitar....

So fit em well and when you think that you have double check.

We clear finish to maybe within .010" of the perimeter and then rabbit the bridge perimeter to match so it sits in a micro pocket of sorts. It also "snaps..." into the pocket so you can rub the bridge over the patch and it "clicks" into position. The click is harder to find, like a weak pulse.... once the HHG has been applied.

Additionally once the bridge is fitted and in it's pocket we double layer masking tape all around and up to the bridge perimeter again making another pocket that the bridge will also snap into once skating on HHG.

We also scrape both patch and bridge in the last 5 seconds before the bridge gets slapped on.

I preheat bridges for about 15 seconds in a 600 watt microwave first. You will find that different species of wood heat up differently too and some get very hot quickly and some not so much.

I don't have a picture right now but we trial fit the bridge including all associated clampage and then tape the clamps in place so once we apply glue all that has to be done is the clamps snugged up they are already prepositioned. With this said we can slap down, position and fully clamp a bridge with HHG in 10 seconds, maybe 5 if we try hard.

Not to poke the bear but Dave we skeptical of the torifaction process and how the altered molecular state of the wood AND.... and fibers would glue in time. I'm not dissing torrified tops or timbers but it does look like we need to learn a new way to glue them properly. Hopefully the benefits will continue to outweigh the trouble.

I have been using Torrified tops a long time and it is a different animal indeed . I don't think it is a fad as it does have its points but it isn't a miracle wood either. With the wood not as absorbent like raw wood , the glue choice and clamping techniques are very important.
Curing glues like tite bond and drying glues like hot hide and fish glue take longer to set and dry so the 24 hr time is important. Also on any wood joint , if you don't have clean wood to wood contact your joint is doomed to failure. Over tightening clamps can also be a problem.
I apply glue to both surfaces make snug and resnug them in about 15 to 20 minutes. Torrified is not for everybody but can be another option. My best advice is if you are not familiar do some clamp tests. I have been using the 192 gram strength for the open time and have not had an issue , but if you feel more comfortable with the high gram strengths use them if your comfortable with them.
Hide glue must be heated and not over heated as it looses its strength quickly if over heated that is why I only use a glue pot. I also like to mix my glue allow to sit a bit then heat it , adding a little water from time to time. I don't like to see the small bubbles in the glue I wait till the vent out and the the glue flows well.

_________________
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

So I got this glued about 10 days ago. So far it's made it through lots of practice and a few performances.

What I ended up doing:

1. Refitted the bridge by scraping it clean and making sure the rabbit around the edge was good.
2. Scraped the top.
3. Put a masking tape dam around the bridge to collect the squeeze out. Got the caul in and the clamps all set for the glue up.
4. Put a heat lamp over the bridge and top to warm it all up.
5. Re-scraped the top and bridge right before gluing it with a fresh batch of 315g HHG. I placed the bridge in position by using two of the StewMac tapered polyethylene locating pins (for new work I use stainless 3/16" pins).
6. Glued it up, clamped it with medium force, cleaned squeeze out like usual and left it in the clamps for 24hr.
7. Reamed glue out of the pin holes and strung it up.

Here's an in-progress shot showing the heat lamp, how I mask off the bridge, etc. One clamp is holding the caul on while the double stick tape works (takes a few minutes) then the clamp was moved so that top area could get warmed up. Be careful if you try this and don't get the top too hot.

_________________
Steve Smith
"Music is what feelings sound like"

Glad this worked for you, thank you so much for posting your progress!
I just bought some 315g HHG after following this thread and will be testing using your process shortly.
I had a couple of fish glue bridge failures over the past couple of years and (per Woodie G) want to eliminate that ever happening again...
Did you put a little paste wax on the outside of the bridge to assist in removing the squeeze-out?

No, the masking tape goes right up to the edge of the bridge so no need for paste wax. As soon as the glue gels I clean it up with hot water on a rag wrapped on a stick about 10" long. After the glue is cleaned off then I pull off the masking tape. The masking tape can be removed fairly easily even with the clamps in place.

One thing you can't see unless you look real carefully is that the curved part of the bridge is masked off first using 1/4" tape that conforms easily to the curves followed up by the 3/4" tape.

_________________
Steve Smith
"Music is what feelings sound like"

Steve we would look at this and also say what Bryan said that you nailed the glue-up, very well done. Maybe that's what torrified needs, nails

Seriously folks look at the bottom of this bridge, glue to the edges or very near, very neat work exploiting the entire bridge foot print for glue-up. Look too at the uniformity of the glue layer, outstanding. This top didn't want a bridge it seems....

Might be a crying shame if the hoped for benefits tonally of a torrified top are negated by having to use JB Weld and 1/2" lag bolts to keep the bridge on. Kidding of course, kind of...

Not directly on topic, but there's some interesting info in this thread:
https://maestronet.com/forum/index.php? ... in/page/2/

Some interesting ideas in that thread, not sure I agree with all of them. Funny how the violin world and the guitar world seem to be at odds in some areas. For the most part it's all just wood.

_________________
Steve Smith
"Music is what feelings sound like"