Ammonia and Bending

Posted: Tue Oct 03, 2006 9:28 pm • Post subject: Ammonia and Bending

Ammonia is sometimes quoted to help in the bending of wooden strips.

Here is a simple method to use this product:

In a transparent plastic pipe (1), place the strips to be bent (2).

Fold and hold one end of the pipe with a strong clamp (3). Fill the pipe, in accordance with the length of the strips, with some ammonia (4).

Fold the other end of the pipe and hold it folded with another strong clamp (5).

Wait, according to the thickness of the strips, from half an hour to one hour.

Then the strips are placed on a jig (1) reproducing the required curve.

A hairdryer (2) can accelerate the drying of the strips.

After a while (one night approximately), the strips are keeping exactly the curve of the jig.

Bosco PDT_Aliboronz_15

Posted: Tue Oct 03, 2006 9:48 pm • Post subject:

Why didn't I think of that! Thanks Bosco, another fine tip 8) Your illustrations are superb as always. Very Happy

Jim

Posted: Tue Oct 03, 2006 10:13 pm • Post subject:

Why ?
Because you are a scientist A good read

, not me.

Friendly,
Bosco PDT_Aliboronz_15

Posted: Wed Oct 04, 2006 12:15 am • Post subject:

Thanks for the tips.
On the related matter, I noticed that when I use ammonia the wood take the curve of the jig but at the same time it tends to become fragile. Just yesterday I was working with two strip of walnut 1.5 x 1.5 mm previously bended using a mix of ammonia and water, I was fixing one of them lightly bending it to fit in place and suddendly it breaked. The fact is that it was really a slight bend and even more important it was not on the part that was more bended but in a part that was almost straight towards the stern. Also I had the same problem on other strip I bended using ammonia. When I use only hot water the wood is not perfectly bended but it is more elastic and it is easier to manipulate.
Did this ever happen to you? or it is just me that is making some mistakes?

Thanks

Marco

Posted: Wed Oct 04, 2006 6:28 am • Post subject:

Hi Marcor, welcome to MSW

Jim

Posted: Wed Oct 04, 2006 7:25 am • Post subject:

Hi Marco,

as I know Ammonia is changing the internal structure of the connection of the cells in the wood.

The ammonia is used as a solvent, and diffuses into the cell wall structure and disassembles the existing microscopic cell components producing a more pliable wood...as the solvent diffuses out of the wood the wood cell components bond in new positions and retain that shape. Steam does the same job but ammonia plasticizes more completely and quicker.

The reason for the material to plasticize (becomes ductile) after the chemical is applied is that the fiber (cellulose) that is straight in the normal condition shrinks, cause the structure to slack, thus making the material becomes easier to bend. But after the ammonia was diffusing totally out of the wood, the strength of the wooden structure should be the same like before.....
This chemical bending is used since a long time for the furniture production with extreme bended wood. And it would be terrible if the wooden chair would break, exactly at the time you make the last detail of your rigging...... clunk

Posted: Wed Oct 04, 2006 10:00 am • Post subject: Ammonia and bending.

Hi,

May I be allowed to put my thoughts to this. Uwe is quite correct in what he says. Timber has a cellular structure, it is also a natural product. By applying chemicals, of any description to the wood it is in my opinion and purely my opinion, weakened. Also dependent on were the wood in question has come from it may have also been chemically treated at source. Something most of us do not realise, hence the application of other chemicals can only go to making it less stable. I know that many woods are bleached or dyed during and after machining prior to being sold. For what purpose I don't know other than to try and make all the timber seem the same as a selling point. It should not all be the same. Wood is natural and hence never all the same thats what makes wood so beautifully.

Uwe is quite right in referring to the plasticising effects on wood and that it is used in the manufacture of furniture, but we are talking about pieces of timber that are far bigger than the pieces that we use. Another thing that in again my opinion has to be taken into consideration is that wood contains, or should contain, about 8-10% water. Hence it is 90-92% dry, or to put it another way its a sponge. Immerse it in a chemical and it will absorb it very quickly. What guarantee have you that you have removed all the chemical from that wood once you have finished bending it. Basically you have no guarantee that it has all been removed.

If this is the case and I highly suspect that it is, these chemical deposits, irrespective of how weak can and may affect any finishing material applied, or any material such as whipping material can suffer long term. Any fixings can be affected again long term by the use of chemicals. Certain woods have natural acids in them, for instance Oak is a well known wood for this. The use of any ferrous fixing with Oak wood will cause blue black stains to appear next to the ferrous fitting, but not with non ferrous fittings.

The amazing qualities of woods this is what makes them so fascinating to me, hence why I love working with them.

I know that it is a very hard problem as to what to do to get woods to bend and I really don't know the answer other than steam bending. A tried and tested method used for centuries by master shipwrights and joiners, I tend to be old fashioned and I will stick with there methods, after all they knew more about wood and how to "sort" it than I will ever begin to know.

These are purely my own feelings on this subject and I stand to be corrected if I am wrong and I hope that I have not offended anybody with my thoughts, if so then I apologise.

Kindest regards to all and happy modelling,

Keith.

Posted: Wed Oct 04, 2006 11:44 am • Post subject:

hi All
I use amoniax mixed met50% water and that works for me vey well.and remains in form as dry.I dit all bending this way on my San Felipe . I do the mix in a aquarium tube that is fixet to a wooden plank to keep it right. I close the ends ofcourse I leave it there fore a couple hours .it depents on the thikness of the wood.I finds also that you can feel softly to which direction the bending go best .I did this only with walnut.I have no idea haw well it goes with pear,ebony or cherry
Sorry my English is still not so good. PDT_Aliboronz_20

Posted: Wed Oct 04, 2006 10:41 pm • Post subject:

Marcor,

For 1.5 x 1.5mm strips, I use some water and one electric iron.

In this case, they are 5 x 5mm strips which must be slightly bent. Rather than cutting this curve from a board of 5mm of thickness, I used ammonia to bend some strips in stock.

Uwe and Keith,

It is this kind of information that I was waiting for and they are welcome. I looked for them but did not find them. Thank you for having taken of your time to pass them on to us.

On another forum they told about methylated spirit which is better than ammonia and the drying of which is faster. What are you thinking about that ?

The parts I treated were "decorative" not structural ones.

Raymond,

Bravo for your bending work.

Very friendly.
Bosco PDT_Aliboronz_15

Posted: Wed Mar 14, 2007 7:55 pm • Post subject:

Just a small photo to remind that methylated spirit is much better than ammonia for bending wood. Odourless and drying very quickly.

- Five minutes soaking for whitewood.
- Ten minutes soaking for hard wood.
- Alligator clips and the small rope to keep the part in the heart of the container.

Bosco PDT_Aliboronz_15