Reblitz: Glue pots vs glue sticks

[Rob Goodale]

Hot hide glue is made from refined animal by-products such as ground bones and cow hide.  It is similar to the material dog rawhide bones are made of only much more refined.  When hot and ready hide glue takes on a distinctive smell very similar to rawhide bones.  It is non-toxic, easily digestible, and my dogs think it's a great snack when I give them the dried left over glue from the bottom of the pot the next day.  Makes my mouth water just thinking about it, yum yum.

Hide glue is an excellent wood glue and is the old standby that wood workers have been using for hundreds of years.  It is strong, can be sanded without clogging the paper, and is an absolute must for rebuilding vintage player pianos.  Since it must be applied hot it requires relatively fast work.  This is not a particularly difficult task if all the parts to be assembled are ready to go.  It hardens as it cools and therefore the parts can be gently worked with in about an hour or so and have full strength in about 24 hours.  Liquid hide glue is available in well stocked wood working stores and may occasionally be found in hardware stores.  It has urea added to allow it to be used cold.  Cold hide glue is also excellent and strong but it takes longer to dry and has a shelf life.  Some claim cold hide glue is not as strong but I know someone personally who uses it regularly to glue in soundboards and I haven't seen one fail yet.  Pianotek sells refined urea that you can mix with your own hide glue to increase the work time as it cools.  Small amounts can be added until you achieve the proper proportion that you need although I would not add any more than necessary. 

One of the biggest advantages of hide glue is that it dries "glass-hard".  In other words it has no flexibility or softness to it when fully cured.  Other glues such as yellow wood glue do not truly become hard.  Even old yellow glue is soft enough to dent with a screw driver or sometimes even a thumb nail.  The advantage of hide glue drying so hard is that it is an ideal glue for vibration energy sensitive applications.  Any glue that has any degree of softness will absorb vibrative energy and likewise robbing the piano of power.  This makes hide glue perfect for gluing hammers, ribs, bridges, soundboards, and other such critical vibration components.

Hot glue sticks from craft stores are a completely different product,  They are fully synthetic and always flexible cold.  It is designed for low-stress applications and does not have a lot of strength.  Two pieces of wood held together with this type of glue can be easily pulled apart and it is certainly not trustworthy for applications in pianos where components must be expected to stay together for 50 or more years.  Bottom line, it has no practical place in piano work.

Rob Goodale, RPT
Las Vegas, NV


  Subject: Reblitz: Glue pots vs glue sticks


  Greetings, 

        Reading Reblitz"s book, he mentions heated glue pots! Wow! To carry such a monstrostity in your car trunk! I was wondering if craft glue sticks are the same thing; Are they? Also, what is aliphatic glue?

  Thanks 
  Julia Gottshall
  REading, PA
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