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View Full Version : Using Ammonia to Bend Wood: Results



sequoia
01-14-2015, 06:51 PM
I was intrigued by a video of a guy using ammonia to bend wood into tight spirals (see earlier post) and thought it would be fun to run an experiment. Also I am tired of cracking ebony bindings and gave it a try.

Material and Methods: A PVC tube (22" x 3/4) was constructed with endcaps one of which is glued and the other friction fit. A crude bending jig is constructed out of 1/4" plywood and screwed to the bench. The jig is lined with aluminum foil. Ammonia is plain household ammonia purchased in the grocery store.

Bindings (0.250 x 0.080 - plain curly maple, curly maple with bwb laminations and ebony) are dropped into the tube, capped, allowed to soak for 45 minutes and then wrapped in foil. The wrapped bindings are then conformed to the male jig with a heat gun and taped. The male jig is then clamped into the female and allowed to cool. (See pictures). After cooling, the binding is heated again and allowed to cool while in the mold.

Results: Curly maple binding: Nasty, old, dry, highly figured maple turned into rubber after the ammonia treatment. Very pliable. No cracking. Slight discoloration of the wood. Wood quite damp and expanded significantly.

Curly maple with bwb purfling. Same as plain maple binding. Incredibly pliable. NO delamination of the bwb (!). Some discoloration of the white purfling strip. Wood quite swollen.

Ebony: Almost no effect with ammonia treatment. Only slight increase in pliability but similar to heat alone. 2 out of 4 bindings cracked.

Discussion: The use of ammonia to bend wood is well known and used in industry. The method works well with woods high in lignan like maple, but has very little effect with ebony. The effect on oily woods like rosewood or cocobolo are unknown.

This method is definitely useful for extremely tight bends with maple and would be of use to the mandolin or violin maker or other construction where extreme bends are needed. However, it doesn't work well with dense woods like ebony with low lignan content.

Conclusion: A bit involved. But if you want your maple to do a tight 90 degrees or just do a bend without breaking, this is a viable method. Interesting. Has its applications to ukulele construction I'm sure. Does not work with ebony.

ksquine
01-17-2015, 06:14 AM
Cool test. Sounds like its a good trick for maple anyway
Ant photos of the color change?

sequoia
01-17-2015, 06:40 AM
The color change was merely superficial/minor and sanded away. No pictures needed. Just looks like maple... Not sure what the application to ukulele building might be except for maybe a soft cutaway binding job. If I was building an F5 mandolin (which I am not) with that curlicue thingy, I would definitely use this method.