I'm starting to experiment with fuming qtr sawn white oak. The articles say you need the commercial 25% ammonia but I've also heard that household ammonia will also work.
What I'd like to know if ammonia concentrations simply affect the time to achieve the required result or if the concentration affects color tones.
(ie will 5% ammonia achive the same color result as 25% ammonia but just take 5X the time??)
Naaah.
Yes...
.. but it does indeed take longer, and will need to be replenished from time to time. Doesn't seem to affect the color as far as I can tell.
Pretty much. This piece, which I made a few years ago as a wedding present for my nephew, was fumed with household ammonia:
On a bit of a tangent, the diazo prints (think blueprints) that were the standard fare in construction for ages, were made with a high strength ammonia process. You used to be able to buy spent solution from them for next to nothing, or they'd give it to you for free. Now that they've pretty much all switched over to computer printing/plotting, and I'm no longer cranking out drawings, I don't know if a blueprinting shop stills has ammonia based processes. I kind of hope not - that was some nasty stuff.
Stronger is faster - how much, I can't say.
Nice console table, Doug.
R
It depends upon the ambient temperature. The warmer it is, the faster the results. I've done some experiments with both and the household and blueline strength were at the same darkeness (dark caramel brown) after 24 hours. The household never darkened beyond that but the blueline took it all the way to black. Here's a webpage
Long story shot, household ammonia gives a very good color after 24 hours. (For more fumes, put the ammonia in a pie pan and light a votive-sized candle under it)
I did some white oak fuming over the summer and can offer some observations. I had the same 5% vs. 25% question. I happened to have some "Janitor" strength ammonia laying around ( not sure of the percent but it was clearly stonger than household ) I decided to try this first before going through the hassle of chasing down 25%. The color I was after was a deep dark brown. I made a tent for the piece and also threw in some test pieces. I let the piece fume for two days before testing. Putting some BLO on it revealed a markedly darker color but still lighter than what I wanted. I sealed everything back up and checked the next day. I didn't observe any changes. After checking on it two days later it was still the same color as the first test. Since I wanted a much darker color I got some 25% ( had to mail order it ) and put it in the fuming tent. After eight hours there was a distinct change in color. I wanted it even darker and let it sit overnight. The next day it was much darker ( so much that I thought I fumed too much but after oiling and shellacking the piece it was just right ) Based on my observations I would definitely say that the depth of the color attainable is directly proportionate to the %.
Some general observations on fuming. If you need the strong stuff observe every safety precaution. Every danger you've heard about 25% is true. This is really nasty stuff. Full ammonia-rated respirator, thick gloves and tight fitting goggles. I've seen pictures of peoples using fans to direct the vapors away and I personally think that's nuts. I got one stray waft of fumes wearing some vented lab goggles and immediately went out and bought a pair of Speedo type goggles, the kind that seal all the way around. I was extremely impressed by the caustice nature of this stuff. I also noticed that ammonia is very light bodied and easy to spill. Use heavy glass dishes for the trays. I used disposable plastic bowls and managed to spill a little bit.
I fumed two pieces. One was flat sawn and the other quarter/rift sawn. The QS piece had a much more consistent color than the FS piece. I'm not sure if it was the quality of the FS wood but in the future I will probably only fume QS. I hate staining in general and, going forward, this is probably the only way I will color wood . Once you get set up to do this, it's really quite easy and much less hassle than staining. Having a color that you can't easily sand through is a pleasure. I also discovered that the advice about using wood from the same board or tree for the whole piece is valid. The QS piece is a box spindle chair and I ran a little short on the 8/4 board I was using and used some additional wood on the back. The color difference is quite noticable but fortunately in an inconspicous place.
Last observation. When you're actually fuming the wood it will turn an unattractive dingy sort-of-grey color. This is normal. You need to put a finish on to express the real color. Although I wouldn't swear to it, it seemed like my test samples, after applying BLO, darkened somewhat overnight.
Anyway, good luck with the experiment.
Paul
Keep replenishing the household ammonia and you'll see the wood keep getting darker.
You don't have enough information to justify that conclusion -- you didn't run a parallel test in which you added more of the original solution to see how that compared to adding more of a stronger solution. The only conclusion that can be justified on the basis of the experiment you describe is that adding more ammonia increases the depth of color.
These are strictly my personal observations, no scientific rigor implied or stated. Also, I did actually replenish the weaker solution on a daily basis and had the results that I mentioned. YMMV.
Well, household ammonia will take white oak all the way to black, but it takes a long time, and a lot of ammonia.
I did a sample trial using a scrap of oak, plastic bucket, and household ammonia. It really turned out good however I noticed that it magnifies the contrast between sapwood and heartwood.
For my table I've minimized sapwood and tried to match color and grain patterns as close as I could. However there are some areas of color inconsistency in the raw wood.
Is there a way to adjust the fuming technique to get a little more darkness in the lighter colored wood so it evens out in the end? I heard something about using tea to force a little more tanin into the wood so it darkens more.
Does this imply I can rub a tea bad on the sapwood to get a little more darkness out of the fuming process??
TIA
Dunno... but be aware that the tea will impart some color to the wood as well. You might be better off adding pure tannin directly -- it's available from any place that sells wine-making supplies.
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