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Glue Performance

Question

What are the important differences in performance between yellow glue, liquid hide glue and traditional flake hide glue for furnituremaking?—Jim Bradley

Answer

John Whiteside replies: Regular Titebond is a good, general purpose woodworking glue. It is strong and dries in about 4 hours. However once it sets, the joint cannot be taken apart without damaging the wood. Furthermore, it has limited working time—about 8-10 minutes. Cleaning up squeeze out is tricky when it is wet and apt to mar the surface if done when the glue is dry.

Flake hide glue is a wonderful glue for furniture-making. Its best feature is that it is reversible. By applying heat and moisture you can take the glue joint apart with no damage to the wood. Another great feature is that it actually draws the joint together to a certain extent as it dries. Also, the dried glue is hard, as opposed to the rubbery quality of dried yellow glue. This hardness quality is especially desirable in guitar making because hard glue joints conduct sound well, whereas rubbery ones dampen sound transmission. Also squeeze-out is easily cleaned up with a wet paper towel.

On the downside, hide glue is not as water resistant as yellow glue. It also has to be mixed by dissolving the flakes in hot water (not to exceed 150°). It has a limited working time, though that can be extended by heating up the joint to be glued.

If a long working time is critical, consider fish glue. Its working time is 40 minutes! I ran a series of joint destruction tests and it surpassed Titebond yellow glue in strength. It dries super crystal-hard. It is reversible. Drips and squeeze-outs are a cinch to clean up with a wet paper towel with no effect on the wood other than raising the grain. Fish glue’s big weakness is that it has almost no water resistance.
Don’t bother with liquid hide glue.

Bruce Wedlock replies: The main difference between traditional hide glue and modern glues like Titebond yellow glue is reversibility. A hide glue joint can be disassembled by application of heat (140°F), denatured alcohol or warm water, allowing for furniture repairs. Modern glues can’t be taken apart. Liquid hide glue has some urea added to make it remain liquid at room temperature. For furniture applications it performs the same as hot hide glue, but requires a longer clamping time.

The glue used for laminations depends on the bending stress. Flat laminations have no stress, so any wood glue will work. If you are making a bent lamination, then stress comes into play causing the joint to creep. The best adhesives for minimum creep are urea formaldehide glues, like Unibond 800 or Weldwood, or epoxies like West System 105 or System Three. Old fashioned hide glue is also very creep resistant.

Bob Oswald replies: Titebond yellow glue is a somewhat permanent adhesive, used primarily to bond wood pieces together in a permanent fashion. Different formulations provide more strength and varying water resistance. I don’t find the strength variations to be significant as the basic Titebond is incredibly strong if clamped well on clean and good mating surfaces. Water-proofness is more significant and for outdoor applications you’ll want to go with Titebond III. For all my furniture applications I use the least expensive Titebond (original). But these are all for permanent applications where I never want the project to come apart again.

Hide glues are heat soluble, and are typically used in making musical instruments where a future repair requires taking the instrument apart. This is done by heating the joint. You would definitely not want to make a thin, delicate musical instrument that could be more easily damaged than a table out of a non-repairable glue such as yellow glue.

I can’t comment much on liquid vs traditional flake glue other than to use a parallel in shellac. That is that purists want to mix their own perfect blend from flakes while the get it done folks use premixed. Being in the camp of 80% solution solves 80% of the problems, I don’t waste time with mixing and blending. On the other hand I would never say that it’s not worth it to mix your own if that’s what you prefer.
Al Breed replies: I use hot hide glue for everything. The disadvantage is that you need to have the stuff warm for it to work well and it has a pot life. However, the advantages are:

  • It’s as strong as epoxy (according to Don Williams at the Smithsonian)
  • It’s easy to clean up with warm water
  • It’s reversible with heat
  • It won’t resist finishes like yellow glue
  • It will hang on for hundreds of years
  • In veneering, it will help fill the pores and is reversible if the veneer shifts.

Guy Senneville replies: Yellow glue certainly has it’s place but is a totally different product than hide glue. I will assume that you are familiar with Titebond and it’s property’s.

Liquid and granular hide glue are very similar to each other. The liquid has a much longer open time as it is formulated to stay liquid in the bottle. Also no heat is required to apply. It is applied in the same manner as yellow glue right out of the bottle. Granular must first be made liquid by adding water then heated to about 150°. and held there during use. It gains it’s bond as it cools. I like hide glue because it is easily reversible if the need arises. That said, it is subject to failure if moisture is added to a joint. Other than Titebond 1, this family is resistant to moisture, some more than others. One of the best features of hide glue is that it can take dies and stains unlike yellow glue.

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