The Society of American Period Furniture Makers

Tools and Techniques => Period design and construction => Topic started by: Phil Hirz on March 11, 2011, 02:22:19 PM

Title: Liquid Hide Glue
Post by: Phil Hirz on March 11, 2011, 02:22:19 PM
Since there were so many great responses to the post on getting started with hide glue I figured I would continue to stir the (hide glue) pot and start a discussion of liquid hide glue.

I have purchased several bottles of Old Brown Glue over the years and I think that Patrick Edwards makes a fantastic product.  However, it is relatively expensive and making liquid hide glue at home seems to be a fairly simple endeavor, especially if you are already set up to use hot hide glue.  So my question is why does it seem that so many people who use hot hide glue will purchase liquid hide glue when it seems so simple to make it yourself?  Making your own liquid hide glue will give you the freshest possible glue and you can make it in any quantiy - thus avoiding spoilage.  Liquid hide glue only calls for normal hide glue and one additional ingredient.  Most people, including Patrick Edwards, suggest using urea.   However, many other people recommend using plain old table salt in place of urea.  One proponent of table salt is Don Williams (see Woodworking Magazine Winter 2009).  I highly respect Don?s opinion in this area since he has an extensive knowledge of furniture restoration, period finishes, and chemistry; plus he is a fellow SAPFM member.

So for those of you who use hot hide glue, but still purchase liquid hide glue - why?  For those of you who make your own liquid hide glue, what is your formula - urea or salt, ratios, etc.?

I am currently experimenting with a formulation of 30% table salt by weight relative to the weight of dry hide glue.  The results so far have been good.  I plan to write some more thoughts on this subject on my website later today (  I started writing it here and it just got too long.

Looking forward to your responses,
Title: Re: Liquid Hide Glue
Post by: Jefferson on March 12, 2011, 09:58:35 AM
Timely post.

Yesterday I bought a couple of clear plastic squeeze bottles, you know like diners use for ketchup. Anyway I intend on trying a batch of liquid hide as I get tired of buying the store bought stuff and throwing half of it away.

I may give the salt recipe a try, I have salt, I don't have any urea.

Title: Re: Liquid Hide Glue
Post by: albreed on March 12, 2011, 01:24:32 PM
Why not just use it hot? It's not that big a deal-Al
Title: Re: Liquid Hide Glue
Post by: Jefferson on March 12, 2011, 03:51:03 PM
It gives you more open time, which can be handy at times. I know for long stretches of stringing I'm not going to use hot hide, I want to make sure it's seated in the grove before the glue starts to grab. With the liquid I don't have to worry about it.

I use hot hide probably 95% of the time, but the other 5% exists and I don't wish to resort to yellow glue.
Title: Re: Liquid Hide Glue
Post by: Phil Hirz on March 12, 2011, 03:58:21 PM
My shop only gets up to the mid 50s during winter.  I use hot hide glue when I can.  However, the open time is only a minute or two at those temperatures.  I'm sure I could improve the working time by warming the joints, gluing up inside where it is warmer, etc. but that is a hassle.  I was planning to add an additional heater to my garage shop this year, but I never got around to it.  Maybe if I install an additional heater next year then it won't be as big an issue.  Still, it seems that there are times when a longer open time is a huge advantage.

Do you manage to get all your glue ups together with hot hide glue?  If the answer is yes are there any special strategies that you employ?

Title: Re: Liquid Hide Glue
Post by: Phil Hirz on March 12, 2011, 04:00:31 PM
By the way - I updated my blog with a new post on liquid hide glue, some research on formulas, and a salt formula experiment I am trying out.

Title: Re: Liquid Hide Glue
Post by: Jefferson on March 12, 2011, 04:26:26 PM
Phil, nice write up.

My basement shop can get pretty chilly in the winter too if I forget to turn on my heater, plus there are just times when more open time takes some of the inherent stress out of some gluing operations.

I'm going to try your salt recipe here in the next few days and see how it goes. We can compare results over time.

Nice job on the blog too by the way.
Title: Re: Liquid Hide Glue
Post by: HSteier on March 12, 2011, 11:27:34 PM
I've been using Franklin's liquid hide glue for a couple of years. It's inexpensive, $12.50 for 16 oz. at Woodcraft. I started using it after I read a research paper from Winterthur that compared hot hide glue with Franklin's cold glue. They found no major difference in strength. The advantage of cold glue over hot hide glue is you don't have to hurry. The cold glue doesn't gel but dries slowly through evaporation. It's great for complex glue-ups.

Howard Steier
Title: Re: Liquid Hide Glue
Post by: dkeller_nc on March 13, 2011, 09:14:22 AM
Phil - I've a background in chemistry (PhD, Chemical Engineering).  One comment I'd make with the salt formula is the possibility of migration.  So long as everything is kept perfectly dry (the project after completion, not the build process), everthing should be fine.  However, sodium chloride is extremely hygroscopic - that is, water loving. 

Large humidity swings could cause such a large amount of sodium chloride in the applied glue to migrate into the surrounding wood, and possibly the finish.  Whether this will actually happen is impossible to say - it would sensitively depend on the wood, the humidity swings, the temperature, and many other factors.  My guess is that this potential would be the most problematic when a fairly large amount of glue has been used in an application with close tolerances.  A veneered surface and a mortise and tenon joint with a substantial amount of glue squeezed out at the bottom of the mortise would be examples.

A related concern is that I would keep this glue mixture far away from any iron or steel hardware - there's little doubt that such hardware in contact with the glue would corrode rather quickly.

Whether any of this is an "actual" concern is debateable, since it would require chemical analysis to determine whether a 200 year old joint actually had a hide glue/salt mixture present, and few museums or antique owners would permit large-scale dismantling and testing of their pieces to find an historic use of liquid hide glue.
Title: Re: Liquid Hide Glue
Post by: Jefferson on March 13, 2011, 01:57:27 PM
The Franklin's liquid hide is a good product, it comes with an expiration date which should keep one out of trouble.

I also, after doing some reading via google, ran across several references of using salt to slow the gel time of hide, seems it's been an accepted practice for a long, long time. Plus I ran across information concerning adding alum to hide glue to make it water proof. That could come in handy if using hide for outside projects.
Title: Re: Liquid Hide Glue
Post by: albreed on March 13, 2011, 10:24:19 PM
They also added milk to make it more waterproof.
The only things I haven't used hide glue on have been my benches and an occasional long table joint-Al
Title: Re: Liquid Hide Glue
Post by: msiemsen on March 14, 2011, 12:09:53 AM
It begs the question as to how they figured out that adding salt and urea retard the setting of hide glue. Where would the enterprising, albeit lazy, possibly vindictive, apprentice find these components, along with warm water, on an early morning as he mixes up the days glue supply?
Title: Re: Liquid Hide Glue
Post by: Jefferson on March 14, 2011, 12:18:37 PM
IIRC, sometimes people add vinegar to hot hide too, but I can't remember where I ran across that or why it's done.

Also, I'd hate to think of what would have happened to the young apprentice if he had been caught peeing in the glue pot.