Techniques with Hide Glue [Picture] - created 10-29-2002
McCafferty, Terry - 10/29/2002.10:37:19
I have resisted for quite some time going with hide glue due to what I perceive to be hassles with mixing, heating, and storing the stuff. I do (especially today) see value in being able to disassemble some critical parts of an instrument though. So here I go to order a glue pot....
I searched the data base, and didn't really find posts related to the tricks of using the stuff. Is there some good technical reading on the subject?
Specifically, at least for now, I am interested in the following:
It looks like I could use the glue pot as a double boiler with water and have a smaller container for the glue. Is this correct and if so, would small plastic cups be good?
For much of the gluing I currently do, I use a small glue bottle applicator that has an accordion type bulb and a 2" long "needle" type tube. The ID of the tube is about .030". Can I squeeze hide glue through this type applicator. Does it seem practical to immerse the applicator in the glue pot of hot water (I guess cap the end) and use it in this way?
I don't glue everyday. Do I have to pour out what is left at the end of the gluing day and start over next time? If not, How do I store it and how do I "re start" it? Do you add water if it thickens? What kind of shelf life does it have?
Finally, in looking at sources of glue, there seems to be several choices. From looking at it some time ago, I seem to remember there is some parameter that has to do with solids content or something that affects grab time, strength,... What do I need for lutherie and where do I get it.
Thanks for tolerating the elementary questions. I hate to spend the time and money lurching into something before leveraging off all your experience.
Oh yeh, what's the best way to get something apart if it's glued together with Tightbond? :?)
There's a lot of information on hide glue in the Library, use the Catalog instead of the search engine and you'll find all your questions have already been discussed.
Here's my Rival Hot Pot (very inexpensive at Target) with a hole cut in the top to hold a glass jar.
I cap the jar overnight if I'm going to be working the next day. For longer periods, I freeze the glue in a zip-lock bag. Sometimes you get a brownish scum when you rewarm it--I just skim it off.
I add water if it gets too thick.
You might have problems putting hide glue into an applicator bottle because it wants to cool and gel. I just brush it on. But keeping the squeeze bottle in a hot water bath is worth a try. The only problem is that the working temperature of the glue is up at the higher end of the comfort range (or the low end of the pain range).
Anyone know where to get a dial thermometer with the appropriate temperature range? The ones I've seen for kitchen use are for oven temperatures.
One of those small Taylor cooking thermometers is fine--room temperature to boiling. I just happened to have this big old Taylor laying around. Actually, any skewer-type meat thermometer covers the range you need.
I have a Timex clock/alarm/temperature monitor with a separate probe originally made for kitchen use which was very inexpensive and works fine for hide glue use.
I use my old Taylor darkroom thermometer.
I have several of those Taylor kitchen thermometers. It's a darn shame they don't all agree on the temperature.
The squeeze bottle doesn't work well. A brush is much better and can be left in the glue and will soften when heated again and gives much better control. Hal..Some Taylor thermometers can be calibrated. Is there a nut on the back side?
I use a squeeze bottle to keep my hide glue. I have an electric pressure cooker which has an adjustable heat control. I plug it in, set the squeeze bottle in the water, and get it when it is needed. I only turn the heat on about 10 minutes before I use the glue. If the opening of the squeeze bottle is too small, cut the tip a little larger.
The first bottle I used was a honey bottle left over from the kitchen. I purchased some others from Laboratory Supply.
As I use up a bottle, I then fill another up.
If it is too thick I add a little more water and get a different texture.
I have tried using a brush, but end up using my fingers mostly. I use the squeeze bottle to apply the majority of the glue in the correct spots, then quickly wipe up excess with my fingers or a damp rag, and spread the glue to the entire surface are which needs covered.
I saw a picture which showed someone using one finger on each side of the guitar kerf smoothing the bead of hide glue which had been applied to the kerfing. This is the technique which I adapted (adopted), and it is the best I have figured out.
I use hide glue as much as I can. Once you get used to a few peculiarities, it has some strong advantages. It is one of the few glues which can be cleaned up on a surface which will need finished, without interfering with the final finish.
I use squeeze bottles, too. I get them from American Science and Surplus, there is probably a photo and a part number in the Library. They are 1 ounce accordian-type bottles, with a cap. They are cheap, you get a bunch for little. I like to fill them up with glue and keep them in the freezer, I take 'em out as I need them.
I use a small squeeze bottle of white glue. I dumped out the white glue, inserted four 5/16"X1" stainless steel bolts as counterweights to keep the bottle floating upright, and fill this little bottle with frozen glue slices that I've made in large batches. I drop this bottle in a hot water bath(the little Rival pot). At night, I take the bottle into the house and keep it in the fridge ; next morning, it goes back into the Rival.
Works great, way faster than a brush, and with the adjustable twist cap, I can regulate the flow of glue for any size bead I need.
The bolts also hold heat, so I can walk away from the pot, or set the bottle down for a few minutes if I'm gluing allot of little pieces.
I'll never use a brush again, except for cleaning up the squeeze out
Make up an ice bath in a styrofoam cup; about 1/2 ice and 1/2 water. Let it sit with the thermometers in it for about 2 minutes. Check to see if they are reading 32 degrrees. If not, hold the hex nut with a wrench and _firmly_ turn the dial body to make the pointer line up with 32 degrees. Put it back in the ice bath to see how close you have come. Continue adjusting until it's dead on. Reportedly, that's how they do them at the factory. The actual temperature at the upper end of the scale isn't that critical, but at least you won't freeze your vegetables at the lower end of the scale.
Great idea on the bolts as a ballast and holding heat. Thanks, I'll give it a try. Ordered a pot and glue yesterday so should be up and cooking by next week.
Deb, I did do the library thing rather than a search. Much better and a lot of good organized info.
Is it better (from the point of view of finishing later) to clean up squeeze out immediately with wet rag,... or let it set a bit and scrape it clean. I don't want to create extra work and catch grief from the sanding and finishing department (read as wife) :?)
Immediate clean up can be done with a dry paper, cloth or wet cloth, or hot wet cloth.
At about 10-15 minutes, the hide glue is rubbery, and can be peeled away with a dull chisel, dull knife or plastic scraper. Any left over can be removed with rubbing with a damp rag at this time.
At several hours, the joint is stuck together tightly, and the excess can be chipped off with a chisel, sanded off with sandpaper, or filed down, etc. Any excess can be scrubbed off with cool or warm water and a rag. Since the joint is tight, putting a damp cloth on the surface does not really allow significant moisture to get into the joint to weaken the joint.
The tidiest appearance and ease of clean up is always done early.
Starbucks sells a dial thermometer that goes from 60 to 220 degrees F, and it has centigrade markings as well.
I use a cheap candy thermometer from the supermarket. Fragile, but I've only broken a couple over the years...
And there are lots of inexpensive electronic thermometers.
I have been using, coincidentally, the same Rival Hot Pot as Bill Machrone. $9.99 - hard to beat. And I notice that Bill has his set on low in the picture. That brings mine to 150 degrees.
I have read just about everything in the library on glue, and still have one question.
A book I've used says to make the glue thick enough that it runs from the brush, rather than drips. A post somewhere on this site says to make the glue like muddy water for violin making. Muddy water drips. It doesn't run. But it seems to drip down from a joint when making a top or bottom (like in the book picture), which thicker stuff doesn't do. So, I'm wondering... How do I know when my hide glue is of the right consistency?
Thanks for suggestions. BTW, I'm making my donation to the site tonight. I am a newbie in violin making, and this site has been incredibly valuable.
The best way to figure this out is to experiment with your glue by gluing blocks of different woods together with different thicknesses of glue, letting dry, and then breaking them apart and looking at the joint strength. For instrument making you use different dilutions for different jobs--very thin for gluing on tops, thicker for blocks, etc. Which book is recommending 'running' glue? Different books have different value-ratings. :-)
I was always concerned about this question. Generally, I mix the glue, and if it is too thick, I thin it down a little. If it is too thin, I leave the bottle open in the water bath for a while, or mix a new batch.
For pore filling, I thin it down a little.
My quality control is non existent. I have built 5 guitars, and done lots of repairs with the hide glue, and have not had any failures. I suppose I am used to the consistency I want to use.
The truth is that the hide glue is very forgiving about consistency and quite reliable.
Your glue is. :-) The point about experimenting is getting to know the particular glue you have, they are all rather different. I've used glue that was pretty finicky, and I've used glue that was very forgiving, it all depends. Also experimentation allows you to check the functionality of your techniques for particular situations or materials--i.e. end grain, rosewoods, etc.
"For pore filling, I thin it down a little."
What chu' talkin' 'bout Willis?
Hide glue for pore filling?!?!?!?! Someone clue me in here. There is a technique for filling pores with hide glue? I'm getting acquainted with the stuff right now, and that is the first I've ever hear of using hide glue to fill pores.
Some violin makers have used hide glue as a sealer under the finish, or mixed with various materials as a filler. Some people say this is a bad idea because the glue is moisture-sensitive and you can end up with problems in your finish if the instrument is exposed to high humidity. I don't know how much of a problem this really is as I know some pretty reputable modern makers who have used a glue ground at times. There are folks who've used alum to moisture-proof their glue in an attempt to avoid the problem.
Yep, Pore filler too.
I finish with French Polished shellac, and have not had any moisture problems with using the hide glue to pore fill.
When I do this, I use a flexible plastic to move it around over the surface, similar to using a credit card, but a little more flexible.
Thank you Andres and Steve.
Well, I'm ashamed to say that I re-read Johnson and Courtnall, and they do say that the glue shouldn't run down the wood. The picture I saw must have shown excess glue brushed onto the joint running down the wood, rather than squeaze out glue. Confusion on my part.
Anyway, I do think your point is a good one, Andres. The endpoint is a joint of a certain strength, not the length of your glue runs. So testing the strength seems sensible. How long do you wait after gluing to test. Seems like if you wait too long, even with a poorly glued joint, it will seem very hard to break apart. The difference between a lot of force, a whole lot of force, and serious force might be hard to differentiate. Do you test after only a few minutes?
Wait until the glue is dry. Overnight to be sure, but in some circumstances 6 or 8 hours will do. The standard of value here is what breaks first--the glue or the wood. For most instrument gluing jobs you want to see the wood splinter out over most of the joint. But for top gluing of a violin you want the glue to go first.
I've been working on gluing up a top and back and I found a couple of things....
The first ones that I did when they were dry you could hold them up to the light and see the seam, after tearing my hair out what it turned out to be is the glue was too thick and was gelling in before I could fully pressure the plates together in my jig. I did discover that the joints were VERY strong when I had to re-do them :)
What I ended up doing was thinning the glue a little and using a hot air gun to warm the joint as I pushed it together on the jig, even before I pulled it off I could tell that the joint was much much tighter. By doing that the joint was able to fully mate and I got a nice tight joint.
Heating the wood with a heat gun has really helped my hide glue technique a lot. I don't believe I've had a glue-up go bad since I started preheating the wood.
I like using worklights for pre-heating unless the shop is particularly cold.
Thanks for the advice, Andres. My joints are strong, holding up to the test. Having read the above though, I'm now wondering if I'm doing things right. I can see the seam after doing a rub joint followed by clamping for a back. I'm not sure how one could be seamless since there is glue in there after all. I figured I had pressed out excess glue pretty well when the friction built up in the joint before clamping.
That's the problem that was driving me crazy, if you can see light through the joint then you can see it in the wood, the heat gun melted the glue enough that what did not soak in the wood pushed out of the joint....
Try this next time:
Apply your glue in a small bead (on tops and backs you don't need much) and clamp your pieces, then take a blow dryer or heat gun and start going up and down the join to get it nice and warm while slowly adjusting the pressure on the plates, on my joints they start snugging up with a small glue bead pushing up and after just a few short minutes I can see from the top that they are very tight. When I pull them off the board later I can't see any light at all through them and boy are they strong.
It took me a few hit and miss tries to figure it out but I am very happy with the results, when I do the braces I'm going to do what hal suggest and get all the wood nice and warm and then clamp them down, that way I know I'll get a good tight joint.
The only thing I need to adjust for now is to get the two plates perfectly flat when glueing, on the top I ended up with a small step between the two plates, I can plane it down but I think I need to modify my glue-up board to clamp vertically to hold the pieces flush. There wasnt' a whole lot of pressure on the joints I think that the plates where just not perfectly flat.
Should be an easy thing to fix :)
Since I initiated this one, guess I should give a brief report back. Last week, I got the pot and glue in and mixed up a sample based on their recommendation. Viscosity seemed to look reasonable to me. Over the weekend, I glued an instrument together. With all the great ideas from the forum folks, it went real easy. I didn't get too aggressive on how much I glued up at once and got everything ready (clamp settings and all) before applying the glue. I did try a squeeze bottle and it worked OK too. I just kept it in the water bath until ready. Being a bit paranoid, I did experiment at first with preheating the parts with a hot air gun first but found this unnecessary as most of my glue-ups required less than 30 seconds to get the glue applied and clamps on.
Looks like I spent a bit too much time worrying about converting to hide glue as it went pretty much without a hitch on the first instrument.
Thanks again for sharing your experience.
In your post #36, I am not sure if you are having problems with joining the top plates together and the back plates. For what it is worth, here is what I do.
I use masking tape, and strapping tape to hold the pieces together.
I apply the masking tape to the length of the seam on one side of the boards. I press it down firmly to bond it to the boards. I tip the joint open a little ways, and tape the strapping tape from side to side on the first side, in about 4 places. As the boards are laid flat, this puts pressure on the joint.
At this point, I turn the boards over, open the joint and place something under the boards, and then put hide glue in the joint.
I lay the boards flat, wipe off the excess glue, place masking tape over the glue joint, and tape with strapping tape horizontally.
I inspect carefully to make sure the pieces line up adequately. If not, I push them until they align well, and weight the areas that need weighting with hammers, boards, planes, etc.
I always leave these alone over night before untaping.
This is a quick way to join the plates for the tops and backs, and the open time on the hide glue is just 15-30 seconds.
I went back to my violin back that seemed to go well, but had a visible seam. I took it apart, then tried many times to clamp it dry RELIABLY so that there was absolutely no seam on the outside surface. I found that to be very hard in and of it self. So I abandoned the clamps, made sure that the joint was a perfect match, and did a rub joint with careful attention to making sure I applied some pressure to closely appose the outside edges. It worked fine - strong and no visible seam. I'm going to ignore my book's advice that backs should be clamped from now on.
I just found the sweetest deal on a very nice little electric hot pot, perfect for a hide glue pot.
I always talk about my favorite surplus place, American Science and Surplus. They offer this item, part #34168. It's priced right, believe me!
They also offer the little squeeze bottles that I like so much to fill with glue and freeze.
Thanks Mark. I just ordered one and some of the little bottles too. I assume you would fill the heater with water and then drop one of the bottles filled with glue in to heat up?
That's how he showed me. Make sure the cap is on tight.
Yes, that works, but I have been using a smaller jar suspended in the actual pot. It seems like it's easier to keep clean, and I used to use the Rival pot like Mario uses and the heating element is erratic in that one, so with that type it's better to use a "double-boiler" type setup. I don't think it's needed with this one, it's very gentle and holds its heat without rapid temperature change. It's made out of metal and is well-constructed.
My rival pot was very erratic at first, too, until I discovered that keeping it at least 3/4 full was the trick. It now holds 145 all day long...
Hey Mark, what part # is the little glue bottle? I ordered one of those pots too, it's awful cheap (price), I hope it's not too cheap (quality). The thing I really wanted was an assortment of those magnets, so I went slightly nuts. We'll see how it all goes. That catalog is a fun read, sort of like Mandolin Brothers.
Well, I checked for the squeeze bottles and it looks like they are all gone! Such is the way of surplus. I am going to try Marios' idea of using an old Elmer's bottle with a bolt or two to wiegh it down and keep the glue warm as well.
As an off-topic point, I really like the carbide rotary rasps, #23437. They fit great in a dremel tool and can be used for anything including inlay routing. They are very good.
I have 4, one inch long, 1/4" stainless steel bolts in mine. The bottle was originally "LePage" white glue. I like this bottle because it has a twist cap that not only seals tight(I mean tight! if I forget to crack it open a little before warming the glue, it turns into a small balloon
I ordered the pot also. This looks like a good find and price.
I got my squeeze bottles from "Lab Supply" or some such company.
why do so many people prefer sqeeze bottles to brushes. A brush has enabled me to spread the glue quickly and evenly. Do you follow up the bottle with a brush?
Dunno about your brush, but I couldn't find a brush that could hold enough glue to load both 18 inch long X braces in one stroke, or for that matter, go around the perimeter of an entire mandolin or guitar.
With a bottle, I can just lightly squeeze it, and out comes a perfect bead of glue, and I never need to stop to re-load(like I would need to do with a brush). Another really great benefit of the bottle is that a bead of glue doesn't cool off as quickly as a thin layer that's been brushed-on, giving you a longer open time.
And no, there's no need to brush the glue after laying the bead. When you join the two pieces, the glue will spread out on its own. For large pieces, like end blocks and such, I use the tip of the bottle to spread the glue around a bit.
I've used a brush, but will never do so again.
When I need to spread glue I use pieces of plastic which come with certain types of x-ray film. These are white, moderately stiff, and easy to cut with a scissors I make little spatulas, with points, curves, wide and narrow edges. This allows me to dispense the glue with the squeeze bottle and then push it where I want quickly.
After all of the previous comment, I usually use my fingers.
(I have used a brush but quit after the first try, and won't try it again.)
I've just started with hide glue, so this thread has been very helpful, and I wanted to share the technique that I've come up with. It's just a bit different.
After looking at Frank Fords' website I saw that Mr. Ford recommends 1.8 to 1 water to dry-glue weight ratio. I tried that and got a few jello chunks, so I just rounded up to 2 to 1.
I'm doing this:
* Put 3 grams of glue grinds int a 10ml syringe (almost exactly 4ml of volume)
* Push the piston all the way down over the grinds
* Stick the nozzle of the syrings into DI H2O and suck up 6ml (same as 6 grams). The water rushing in mixes with the grinds very well making a homogeneous mix.
* This puts the syringe piston at 10ml, there is a bubble and about 9ml of glue-gel in the syringe.
* Cap the syringe nozzle
* Put this syringe into the Freezer till I need it.
* When I need it, dunk the whole syringe into the hot water bath and use.
This way, I have the ease of use of a syringe, the glue is in self-contained small amounts; measuring, storage, heating and dispensing is all done with the same syringe.
Also, the syringes are re-usable and if you want to get fancy and add needles, tubes or other tips, there are a wide variety of things that fit on a standard syringe nozzle.
DI is de-ionized water.
Chuck, It sounds as though you are not cooking the glue to any extent. I have read that heating up the glue to 145 degrees F for a period of time allows the glue molecules to aggragate and get longer which supposedly makes the glue stronger. Something to think about.
How long is
...145 degrees F for a period of time... ?
As I said I'm totally new at this so any help is much appreciated.
The instructions from Frank Ford (where I bought my glue) said to cook it until it gets clear. My glue never really got clear, but it did look more even and smooth after about 15 minutes. Now that I think about it, I think the story goes that the strength developes during the cooling process after it has been cooked the first time. Supposedly, when you re-heat the glue it is much stronger than the first time it was cooked. Does this jive with anyone else's understanding?
I just found confirmation of the "let it cool at least once" idea, a second-hand reference to an old article in Fine Woodworking written by someone who "probably worked in a hide glue factory". --Well it's a start. :-)
Since hide glue is a protein, and I work with proteins all day here at work (even though I'm NOT a biochemist) I am going to make this conjecture.
As hide glue is heated it denatures, or unfolds and becomes more liquid (some proteins, like eggs, do the opposite, they get less liquid). Then as it cools, it re-folds and gels. Since protein folding is a very complex process, it it best to give it as much time to fold as possible. Therefore, it would be best not to put the hot glue directly into the freeze. I would suggest that the glue should be left at room temperature to gel before freezing. Sort of an annealing process.
From personal experience, as long as it is liquified, it will work. I don't think there are any certain cycles it has to go through. I imagined that it was a long molecule, which when in water, stretches out and intertwines with other molecules. As it is heated it becomes more liquid. As it cools, it gels. It is sticky as long as it is liquified. If it is gel, (or dry) it will not be sticky (in other words, not good for gluing).
If it is overheated, the molecular nature of the long proteins might break down. It can be frozen indefinitely and repeatedly. It can be dried repeatedly, and rehydrated. If left at room temperature, it will grow mold (personal experience).
One of the violins schools/courses kept running into problems with plate joints splitting during carving. One of the teachers set out to figure out the problem and ended up assigning blame to new batches of glue made up fresh for those joints.
I read comments by another maker who pointed out that you can get a sense for how the glue is working by letting it gel on your finger tips and seeing how hard it is to pull the fingers apart once the glue is a little dry. He said you can see quite a difference between fresh glue and glue that has cycled.
"He said you can see quite a difference between fresh glue and glue that has cycled"
Andres, which is the stronger glue, the fresh or melted-once?
You can probably put the glue in the syringes and freeze it very much like you do now; just cook it first until it is good and liquid (i.e., none of it should resemble tapioca pudding). Last week, after I got some advice here on MIMF (thanks, by the way), I made up a big batch of glue on the stove in a double boiler, and filled lots of 2 oz. bottles by squeezing out the air, sticking their nozzles into the glue upside down, and letting the bottles expand. This had the added benefit of leaving the bubbly scum in the pan and not in the bottles of glue. I now have a few months' worth of really good glue ready to go at a moment's notice. Your syringes would work better for the sucking part than my 2 oz. bottles.
That is a good idea Don. I am getting some of that scum in the syringes, and it is hard to get rid of. Maybe the best idea is to make a big batch and just fill a bunch of syringes.
Anyone know how to clarify this stuff a bit? I'm using the granular glue from GW and it is milky when liquid. F.Ford says that his glue is clear. Do I just need to buy better glue or is the stuff I got good enough?
I'm pretty sure William Tandy Young said in an earlier discussion that clarity doesn't mean anything - check the Library.
I too use a Rival brand water pot, and I cured the problem of its being erratic. I put a sleeve from a tin can, just larger than my glue jar, in the center, and filled the area outside of it with aluminum chips from a machine shop. This keeps the pot from thinking it has boiled dry, and shutting itself off, and doesn't add any moisture to the air in the shop.
I think Lee Valley has those little accordion squeeze bottles.
BTW, I found the ideal dial thermometer for glue. It's a Taylor made for foaming milk for cappucino. Range is 120-180 F. (apparently best foaming temp is 140-160).
Everyone here seems to be using clamps for their projects? I've been told when using hide glue it is best to spread the glue, join the pieces and place weights on the project as most people will squeeze too much glue out of the joint rather than having enough in the joint to provide the strongest possible joint.
If you have both surfaces covered with glue, it will set quick enough that I have never been able to starve a joint.
On wide surfaces I squirt the glue, then spread it over the surfaces with a wooden or plastic spatula, or by rubbing the surfaced over each other. If you have both surfaces covered with glue, I don't think the joint will ever be starved.
Since I started building guitars (just this last year), I have started using masking tape to align and position boards for gluing. This allows me to work quickly to position and clamp them before the glue gels. If it is a place where there will be a lot of tension holding a larger board or some other odd situation, I use the strapping tape.
It is possible to glue-starve with hide glue. A maker of my acquaintance got rather too good at quicly and firmly clamping his FBs in his early days and had them fall off a few times.
I would recommend a vacuum frame for hide glue as it is very fast and simple to use. I use 315gm glue for bracing which is almost clear and starts to gel in under a minute. The added advantage is that the vacuum clamp provides even, precise clamping pressure over the entire brace and doesn't crush any wood. You can also preshape the brace off the soundboard so that when you're done gluing...you're done. I glue, place and vacuum clamp, shape the next brace(s) and repeat. A soundboard can be braced in about half the time as when using clamps or go-bar decks.
Just wanted to touch base in this thread again. My little idea of using syringes has turned out to be a bust. The one thing that I thought the syringes would be great at, dispensing the glue, is what they suck at.
Seems that hide glue makes the piston sticky in the barrel of the syringe (yes, "firm grasp of the obvious" comes to mind). So, when I'm trying to dispense a nice even bead of glue I get: FLOOD ... nothing ... FLOOD ... nothing ... FLOOD ... You get the point, and the point is USE SQUEEZE BOTTLES.
When I have a full bottle, the glue stays warm enough to use well. When I am at the bottom of the bottle, I have to invert the bottle in the warming water to keep the opening warm and free from gelled glue.
Jim, I often do two braces at a time and it's ready to go by the time I have the next brace prepared. Remember, all you're doing is releasing the vacuum briefly while you position the new brace and wipe off squeeze out.........then all of the previous braces are back under clamp pressure again. It works the same with Titebond or the LMI white glue as well. You can work as fast as you would like, the clamping is never in the way.
What vacuum system do you use?
Mario, I use an ancient Milwaukee reciprocal pump rated for continuous duty. It's pretty loud so I keep it in my spray booth when using it. The vacuum frame is shop built after the drawings in the LMI handbook only a lot simpler. I have a gauge on it to watch the pressure and at our 7000' altitude here in Colorado the best I can get is about 12", where at sea level you should be able to get about 17% higher. I think you can rig up a valve to dump the vacuum faster but I haven't looked into that. It's the biggest advance in my shop since paper towels.
I don't know if this will contribute much to the conversation but I found an interesting article in American woodworker April 1998 issue. on page 54 entitle hide glue. very informative. pg 55 has a table that list glue strengths. mixture ratios for pine and maple. how to extend open time, improve adhesion with vinegar, softer curing glue by adding glycerin and other helpful tips. Big help for those starting out.
Just another note on that "pore-filling" thing way back in this thread. Diluted hide glue used as a first coat on wood is called "sizing". I first discovered it when I got tired of blotchy staining on pine, cherry, beech, etc. The old cabinet-makers would spread out some of that stuff, sand it smooth, and then apply stain right on top of it. Bye bye blotches...
Works great. Hide rules.