Replies

1. 
   CStanford_ | Jul 27, 2000 09:49pm | #1

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   Chuck, I'm a bit surprised at the question. Hot hide glue should never be reused. You'll need to mix and warm a new batch for each work session. Cold hide glue is available in bottles from Franklin International (the Titebond folks) and has a shelf life of about one year if kept in climate controlled circumstances. Every mail order woodworking supplier of any repute carries the cold hide glue product I mentioned.

1. 
   William_Tandy_Young | Jul 28, 2000 02:14am | #2

   *Chuck:There's no need to make up a fresh batch of hide glue every day. I don't, and most of my colleagues in the museum conservation field don't either, and believe me, they're fussy individuals!There are some folks who feel it's critical to make a new batch of glue every day. They're certainly entitled to their opinion. I'd rather see them do that than do what some old timers proudly do, which is to keep adding fresh glue to an old existing batch of glue for months on end. That is not recommended.Anyway, you can always put a lid on the jar and stick the glue in the fridge between uses. Common practice. Or, you can add a preservative, which is completely legit. You can buy packets of powdered fungicide at agricultural or garden supply stores--it's sold as a preservative for water that is being held in storage tanks. 1 teaspoon of powdered fungicide per quart of mixed glue does the job. (This mix ratio courtesy of FWW Contributing Editor Chris Minick).Here's the trick part of the answer, though. The fungicide also acts as a gel depressant, so your glue will take longer to gel and harden after you apply it. To answer your question in the most complete sense, then, you can prevent glue spoilage, but not without altering the glue's performance in one way or another. Another strategy is to make sure that you're using high grade glue. Poor quality glue spoils more quickly than the good stuff, because it hasn't been manufactured with the same level of care and control. The premier manufacturers of granular hide glue add zinc sulfate as a preservative when they formulate the glue, so it will have a longer pot life than the average quality glue. Finally, a little perspective. There are a ton of centuries old hide glue joints in the world, still holding strong. The guys that made those joints had to make their own glue from scratch (yum!). Do you think they were using clinically approved pure lab grade hide glue every minute of every workday? Most of the time, they probably dipped into a glue pot that you or I wouldn't go within ten feet of. And the joints still hold. Hide glue is tough stuff that doesn't scare easily. They don't call it animal glue for nothing.Hope this helps. Good luck.

1. 
   Bob_Berner | Jul 28, 2000 02:12pm | #3

   *Here's a hide glue question. How resistant is cured hide glue to mechanical shock? Does it fracture easily or is it very tough? I was planning on using it to attach the handle to a Large mallet, shall we say a big persuader?, I am making and was wondering if hide glue would work. This is just something that I am fooling around with, not an heirloom tool or fine furniture. I had considered using epoxy, but they can tend to be brittle and are of course non-reversible. Any advice is greatly appreciated. Bob

1. 
   Stephen_Shepherd | Jul 28, 2000 02:59pm | #4

   *Chuck,You can preserve your hide glue by placing a stick of willow (any willow will do) in the glue pot. Strip off just the outer bark, leaving the inner bark that contains high concentrations of salicylic acid which will prevent mold growth. An asprin will also work.Stephen

1. 
   Stephen_Shepherd | Jul 28, 2000 03:02pm | #5

   *Bob,Put a drop or two of glycerin in the hide glue to make it more flexible for this application. The advantage of hide glue over epoxy is that the hide glue may come loose and you can re-glue, the epoxy will break the wood.Stephen

2. 
   CStanford_ | Jul 28, 2000 04:23pm | #6

   *I'd still be scared of using leftover hide glue, preserved or not, in a structural joint. Maybe this is not an issue when re-attaching veneers and small parts. I would never trust anything but a fresh batch if reworking a rail to leg attachment or something like that.FWIW, the cold hide glue product is fantastically convenient for little veneer repairs and gluing small parts, and should even be strong enough for heavier duty work.Over the years I've managed, in spite of my stupidity, to estimate the amount of glue needed for most work sessions, so I rarely end up with enough at the bottom of the pot to worry about keeping. Perhaps this is a simple answer to your dilemma. Those times when I've come up a bit short, I just grab the cold glue and I've never had a problem (knock on wood).Good luck..............

3. 
   Drew_Nyman | Aug 08, 2000 11:56am | #7

   *I'm with C Stanford here. Hide glue does tend to lose some strength when reheated. I buy it in 50 LB drums. I do cheat a little though as I sometimes use the microwave to heat it.

4. 
   CStanford_ | Aug 10, 2000 04:33am | #8

   *A question for you hide glue savers - how do you know how much water to add the next day, or the day after, to account for the water lost to evaporation?

5. 
   William_Tandy_Young | Aug 10, 2000 06:23am | #9

   *The viscosity of the glue changes during the course of the workday as it's being kept hot. I check and adjust the viscosity of the glue as a matter of routine at least once or twice a day. If it gets a little thick, add a bit of water. If it's too thin, let it skin over, then stir the skin back into the glue. The viscosity of the glue is a judgement call. Working with the glue daily helps develop a feel for how it's behaving and what kind of consistency it should have. Lower gram strength glues can be used a little thicker since they have a lower molecular weight and gel more slowly.The two worst things to do to hide glue are overheat it (which wrecks the molecular structure)and cook the moisture out of it (which turns it into a caramel-type goo). Electric glue pots keep the temp at a steady 140 degrees so the glue won't overcook. Putting a lid on the pot keeps the glue from skinning over and losing moisture too quickly. If you maintain the glue's temp and consistency carefully, reheating it is fine. However, the last half inch of glue in the jar gets pretty hard to maintain properly (even if you just made it the night before). So when a batch starts to run low I make a fresh batch and discard the reheated stuff or thin it down for use as a size.

6. 
   Sgian_Dubh | Aug 10, 2000 12:27pm | #10

   *Interesting question that brings back a memory or two. Moons ago as a daft wee trainee, one of my jobs was to keep the glue pots topped up and clean. In the workshop, at that time, we would sometimes go through two or three pots in a day, and we had a few pots kicking around as I recall, with more pots than heaters. The darn Scotch glue (as we knew it) was lethal as it came from the supplier. A 2lb or 3 lb brick that we wrapped in heavy cloth to prevent shards flying and then whacked several times with a hammer. I guess we were kind of sloppy in our practices as compared to all the pernickety advice offered today, for it was common to add recently softened glue to old stuff in the pot, and if a cabinetmaker was getting short of glue in the pot near him, he'd grab another from further down the workshop and pour some in. Then I'd get shouted at to fill the pots again, "Pronto, ya glaikit wee git!" and other helpful encouragement. (That's about the politest I can repeat.) The joinery seemed to hold together pretty well as I recall, even though the glue was heated, cooled, reheated, added to, etc.. Still, once a fortnight on 'payday' Friday, it was my job to make sure the pots were all emptied last thing, cleaned, and fresh glue thrown in to enough pots for the available burners, and covered with water to soak ready for use the next week, or the Saturday if we were to do overtime. Payday Friday was the only day that I didn't get shouted at to refill the pots, and guys would go around scrounging glue from any pot available.Well, that's ancient history, but over the last few years I've become less and less enamoured of the yellow PVA stuff. The white PVA is a little better, but both tend to go off too quickly to allow for applying the cramps and squaring a frame and so on in the extreme heat and humidity experienced in this part of the world. I still use them- PVA's, for simple glue-ups, but I'm using Scotch or hide glue more and more for serious joinery. I don't go through glue like we did in that old workshop, so it might be two or three weeks between needing batches. I've found that pouring what's not needed into a covered plastic jar almost to the top, and shoving the jar in the fridge will do a pretty good job of keeping it for weeks, even months. My shopmate is not too keen on the practice, storing my glue next to his lunch and cokes, but the dogs are generally not too far away when I do a glue-up for they are fond of those hot, tasty wee morsels that sometimes drop on the floor! Sliante.

7. 
   jim_fagan | Jan 06, 2001 11:29am | #11

   *AntibioticsIf you have an old prescription use a tablet.But remember you are supposed to take them all til finished. This will also help the rest of use in preventing the evolution of antibiotic resistant strains.Anothjer choise is a single crystal of copper sulfate, maybe 25-50 milligrams.