Replies

1. 
   SteveSchoene | Apr 23, 2008 12:47pm | #1

   The potential problem with this--and with fuming -- is that the process depends on the chemical make up of the wood as well as of the ammonia.  This means that different boards can react somewhat differently to the process, and potentially in ways that you can't prevent by visually matching the boards before hand, unless they all come from the same tree. 

   You can get a very similar look with an analine dye for the base coloring.  The dye will be much less dependent on the particular board, and in ways that you can control by selection of the lumber.   

2. 
   blewcrowe | Apr 23, 2008 02:48pm | #2

   David, how much variation did you see from one piece of wood to the next?

1. 
   ring | Apr 23, 2008 03:53pm | #4

   blewcrowe, Steve, I get what you're saying, and it seems that such a variation would be expected with any dye or chemical reactive treatment, as opposed to tinting the lacquer or some such. To my mind, accentuating the natural variations in the wood adds to the appeal of the project. We use French white oak, and we buy only full slings. You get wood from several trees in a sling, but matching pieces is not hard when you've got that choice in front of you. So in fact, I've gotten pretty uniform results in the experiment.Luckily, I have a pretty free hand in this project and don't need to clear everything with a committee of designers. Actually, you're the committee!If it turns out interesting I'll post pics.regards,David Ring

   http://www.touchwood.co.il/?id=1&lang=e

1. 
   blewcrowe | Apr 23, 2008 03:58pm | #5

   Well David, you've given me something to think about. I'll try it someday. Thanks.

3. 
   RickL | Apr 23, 2008 03:10pm | #3

   I'm no expert but do see the process on a daily basis in our shop.

   A couple of things. White oak has a higher tannic acid content than red oak. We fume red oak by brushing on tannic acid. It fumes better when damp. We also use anhydrous ammonia in a 100 lb tank.

   So go for it. You will have to do some experimenting and if it works then do it. The fuming penetrates deeper and you can penetrate some existing finishes after the finish is applied. In his book George Frank told of darkening a bank interior this way.

   I don't think you will get the depth of a fumed finish. Sounds more like a stain or dye finish than a real fumed finish. Try fuming and your brush on method then cross cut a sample to compare the finish depth. Whatever works is fair game. I don't think you could fairly call it a fumed finish if you brush it on.  You would have to compare the look of your  brush on finish compared to a real fumed finish.

1. 
   ring | Apr 23, 2008 04:10pm | #7

   Rick,I remember that story from George Frank. If I need to darken everything in the synagogue after it's been installed, I just might get to try that trick after all this time.I will do the comparison test you suggest, just to satisfy my own curiosity. Aside from some Knotheads (like me) who revel in such arcane knowledge, nobody involved in this project gives a damn what the finish is called or how it was done. Whether it is actually "fumed" or not will remain a matter between us...regards,David Ring

   http://www.touchwood.co.il/?id=1&lang=e

1. 
   RickL | Apr 23, 2008 06:56pm | #11

   I was talking to our finisher and he doesn't think there would be much difference between fuming or brushing.  We routinely moisten the wood as it seems to speed up the process.

   What's with the vinegar???? You don't need to neutralize anything in the ammonia process.  Vinegar is an acid and the thought is it might lighten the wood. Ditch the vinegar completely.

   You are fuming white Oak not red oak. You will have to add tannic acid to the red oak or you won't see much darkening.

   Edited 4/23/2008 11:57 am ET by RickL

1. 
   ring | Apr 23, 2008 08:00pm | #13

   I had this idea to neutralize with vinegar (acid) because anhydrous ammonia is NH3OH, and I suspected that as a liquid it would be leaving some base residue in the wood.  Maybe it's uneccessary as you say.

   I've got a test case piece in the fuming container overnight, to compare with the brushed pieces I already prepared.  I'll cross-cut a slice off of both tomorrow and compare the penetration.

   Yes, it's white oak, and the darkening is apparent and immediate as soon as the ammonia hits it.David Ring

   http://www.touchwood.co.il/?id=1&lang=e

1. 
   RickL | Apr 23, 2008 09:21pm | #15

   I'm using anhydrous ammonia but you are not. Most ammonia is mixed with water especially the household type and even the stronger industrial ammonia.   Anhydrous means "without water".  Ammonia doesn't leave any residue. The stuff I use is pure ammonia and leaves the storage tank as a gas. 

    We use blue print machine ammonia for some stuff and it's listed as aqua ammonia. Not  sure of the concentration. How did you arrive at the number 25%????? I'm pretty sure the concentration of ammonia is lower.

   Wikipedia...The strength of such solutions is measured in units of baume (density), with 26 degrees baume (about 30 weight percent ammonia at 15.5 °C) being the typical high concentration commercial product.[4] Household ammonia ranges in concentration from 5 to 10 weight percent ammonia

   Edited 4/23/2008 2:29 pm ET by RickL

2. 
   ring | Apr 23, 2008 10:04pm | #16

   It's from a commercial chemical supply house and it says 25% on the bottles.David Ring

   http://www.touchwood.co.il/?id=1&lang=e

3. 
   ring | Apr 24, 2008 06:53pm | #17

   OK, I've learned a few things and thought you might be interested...The attached photo shows 2 pieces of a white oak profile treated with ammonia. The wood is 3/4" thick. The one on the right was fumed in the traditional manner for 24 hours. The crosscut shows clearly that the fuming penetrated some 3-4 mm from all directions. The one on the left was brushed with a 12% ammonia solution (I used 25% ammonia diluted 50-50 with water). Its crosscut clearly shows that it didn't penetrate by anything that the naked eye can discern. Both pieces have a clear finish over the ammonia treatment. The color tones are another issue altogether. The brushed one is much lighter in color. Using straight 25% ammonia would give a darker tone, and fuming for less time would clearly give a lighter tone. So I'm confident that one could achieve more or less the same tone either way. What doesn't come across in the photo is the depth of color to the fuming, which is what Steve has been talking about all along. Bottom line - there's no question in my mind that the traditional fuming gives a quality result that cannot be achieved by brushing ammonia on the surface. However, I'm not ruling that treatment out entirely, since it does have tremendous advantages in the ease of application. Fuming a room full of items of all sizes and shapes seems too difficult if one is not set up to do it safely and easily.Thanks for all the input...David Ring

   http://www.touchwood.co.il/?id=1&lang=e

   
4. 
   saschafer | Apr 24, 2008 08:37pm | #18

   Told you so. ;-)

   -Steve

    

5. 
   doorboy | Apr 24, 2008 11:00pm | #19

   The defense rests"How do you spell illiterate?"

6. 
   blewcrowe | Apr 25, 2008 08:43pm | #20

   Still, David, I'm amazed at what your brushing accomplished.

   Denny

4. 
   saschafer | Apr 23, 2008 04:02pm | #6

   For me, the big advantage of fuming is that the color penetrates very deeply into the wood. That means that you can do the fuming before final milling, so you can cull out any pieces that don't color well. It's more like working with wood that's a consistent color all the way through, rather than just dyed on the surface.

   -Steve

    

1. 
   ring | Apr 23, 2008 04:13pm | #8

   Steve,Let me get this straight - I've got lots and lots of beaded moldings, raised panel doors, as well as outright carving to do on this job. Are you telling me than I could fume the oak BEFORE I do those things?David Ring

   http://www.touchwood.co.il/?id=1&lang=e

1. 
   saschafer | Apr 23, 2008 06:46pm | #9

   I've found that overnight fuming of white oak penetrates at least 3/8" deep. As far as I can tell, the color change is essentially uniform over that depth.

   -Steve

    

1. 
   blewcrowe | Apr 23, 2008 06:54pm | #10

   Wow, I never realized it penetrated like that. It would be interesting to see how penetrating the paint on method goes.

5. 
   AlanWS | Apr 23, 2008 07:01pm | #12

   I would expect that the major disadvantage of painting it on is the water you introduce to the wood. If you have time to let it dry, it should be fine. To help it dry faster, you could dilute your concentrated ammonia with alcohol instead of water. I would not bother with the vinegar unless you are trying to stop the darkening process quickly, since the ammonia will evaporate. It is different from lye in this respect.

1. 
   ring | Apr 23, 2008 08:05pm | #14

   Thanks Alan.  There's no real problem with the drying time.   The weather is quite hot and dry here...

   I guess the vinegar was an uneccessary precaution.  I'll ditch it.

   I'm still interested to see any discernible difference between brushing on the ammonia and conventional fuming.  Tomorrow I'll have a test comparison.David Ring

   http://www.touchwood.co.il/?id=1&lang=e