Fuming experiments – Stonehill Primitive Bows

Fuming experiments

What is fuming?

Fuming is a process not with fire or smoke. Fuming means to treat the wood with ammonia damps. In Germany some wood species are available as fumed wood, for example ‚Räuchereiche‘ which means translated fumed oak. This wood is very dark, it is not dyed or stained, the color come from a chemical process. The Ammonia reacts with athe tannin acids in the wood. The more acids are in the wood, the more drastic is the reaction. Also the temperature seems to be a great factor.

Some woods have more acids, some not. This why some wood species react well to fuming. This are (by my exp.) oak, osage, ash, elm, black locust. I’m sure there are a lot more around.

So what do we need:

  • a pipe, or better a tube, suitable for the whole bow.
  • ammonia in a concentration of at least 10%, better 15 or 20%

The tube is to be fixed on the ceiling or something else and sealed at this end. The lower end should have a removeable cover which could be tightly sealed to the tube.

The bow should hang freely in the tube, so that the complete surface is exposed to the damps of the ammonia. The ammonia is in an open pot inside the tube. If the tube is transparent the changing color can be observed easily, after one day there should be a definete change in color.  I have experimented with different woods and different concentration and different time (1-14 days).

If you have to glue something before fuming: use epoxi, this is the only glue that will not be affected by the ammonia! After the process and after the dampening (be sure there is no ammonia damp inside) out you can use every glue!

 

 

Here are some testings:

First pic shows 3  dogwood staves (left to right)
left: fumed for 5 days with traces of cambium on
middle: fumed for 1 day cleaned before fuming
right: no fuming with traces of cambium for comparison

1

next pic shows fresh cross cuts
l: fume damp has vaporized in the whole diameter
m: vaporized about 6 mm
r: just for comparison, no fume

Here is a detail of the stave in the middle. Forgot to say it was split after the fuming process. Marks shows how deep the damp has vaporized in.

next is a comparison between fuming and staining with iron oxide (something what is called vinegar stain here)
l: BL (from the Mohegan stave) stained
m: osage stained
r: osage fumed for 2 weeks

I used no vinegar for staining but iron chloride – works more aggressive.
The long time osage came out like ebony really cool color.

next a detail of the staining, the fresh cuttings show now color inside the wood. All is on the surface.

detail of the fumed osage, the damp was in the whole cross section

and a pic of the surface

 

I wanted to know how the next ring looks like on that dark piece of osage. See what I found! The pics are taken inside and don’t show the real beauty of that piece. It seems that the damp has vaporized from the sides to the middle. I’m convinced it would be darker if a solution were used or longer time. But anyway I like the result and I will use that technic for sure.

Other thing is, the ammonia treatment has changed the wood structure. Unbelievable how smooth the wood has become.The first pic shows the piece and for comparison a fresh worked osage for comparison.

So what did happen to the wood:

  • A change in color, stable and not only on the surface. This is no dye or stain it a chemical reaction of the tanning acids in the wood.
  • All bugs, borers or other insects were killed for sure.
  • The surface of the wood changes in a silky, very smooth texture. I don’t know why, but the effect is here – I’m sure!
  • The bonding of the wood cells seems to be broken up. It should be proved wether the bow could be bent or corrected this way. The effect of the broken up bonding seems to be reversible, when moisture and damps vaporises out. I always wait as least the same ammount of time before tillering as the the stave/bow was exposed to fuming.
  • When the stave/bow comes out of the fuming pipe it is wet and stinks heavily. After a few hours in the air the moisture and smell is gone.

    Here is a photo shooting of a 5 days fuming procedure:

day 1

day 2

day 3

day 4

day 5

and this was the setup: an old paint can + a foil from the kitchen, I do not know the exact name for it. It is used for broiling in the oven.

Wasn’t pleased with it and got my hands on a thicker plastic tube. Disadvantage is it isn#T that clear like the other, but it does the job.The end with the wire is hanging on the ceiling, the bow hangs freely in the tube on the cord (see my finger), the other end has a matching pot for the ammonia and is just reaching the floor. I think the pics explain all, and I have no need to struggle for more words.
Let know your results guys ….

Comments

Hartmut Kleinjung

Ein staunendes „Hallo“ an den Meister!
ich bin Bogenbauanfänger und komme bei diesen Seiten aus dem Staunen nicht mehr raus.
Zur Ammoniakbehandlung: verträgt sich diese Färbemethode auch mit verleimten (Epoxydharze) Hölzern?
Oder greift der Ammoniak den Kleber an?

    Simon Siess

    Hi Hartmut
    Epoxi + fuming: o.k.
    TB3 (white glues) + fuming. no!
    superglue + fuming: no!

    Good luck with your projects!

Hartmut Kleinjung

Dear Simon,
thanks for your detailed information.
Time has come to try some fuming.
Here ist another question: what concentration of ammonia (germ. Ammoniak-Lösung) do you use?

Kind regards,
Hartmut

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