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Fuming finished white oak

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Forum topic by Greg posted 12-06-2019 02:51 AM 427 views 0 times favorited 9 replies Add to Favorites Watch
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Greg

40 posts in 3299 days


12-06-2019 02:51 AM

Topic tags/keywords: white oak ammonia tannins fumigating oak

Does anyone have any experience successfully fuming white oak that already has a finish on it? I bought a clock that already has a finish on it (assume polyurethane). The finish is lighter than what I’d prefer. I have successfully fumigated QSWO prior to applying a finish on one of my recent projects. What I noticed when I did trial pieces is that the ammonia reaction with the tannins penetrated the wood much deeper than I expected. That’s why I think I might have a chance with the finished clock. Perhaps the fumes will penetrate through micro pores. I thought about striping the clock but some of the wood is sandwiched between the glass and the clock face. The clock is constructed in a way the the space is now inaccessible.
Thanks for your input.

-- Greg - For the benefit and enjoyment of the people


9 replies so far

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ddockstader

179 posts in 3868 days


#1 posted 12-06-2019 07:24 AM

I think you mean “fuming,” not “fumigating.” Fumigating is what you do if the wood has bugs, like powder post beetles. That being said, I believe the finish will prevent the fumes from reaching the oak. The oak has to be fully exposed to the ammonia fumes and a polyurethane finish (or any finish like shellac) will prevent the tannin from reacting with the fumes. Sorry, but stripping the finish is the only possibility if you want to darken the oak with ammonia. That being said, you could try putting an additional finish with coloring, such as a tinted polyurethane, over the existing finish.

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Fred Hargis

5928 posts in 3100 days


#2 posted 12-06-2019 11:18 AM

I can’t imagine that would work (the fuming), but let us know how it comes out if you try it.

-- Our village hasn't lost it's idiot, he was elected to congress.

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SMP

1596 posts in 512 days


#3 posted 12-06-2019 01:29 PM

I have done it with shellac and with BLO already on. Haven’t tried with poly..

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Greg

40 posts in 3299 days


#4 posted 12-06-2019 05:24 PM

Yes, fuming. How were your results with shellac already on?

-- Greg - For the benefit and enjoyment of the people

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therealSteveN

4645 posts in 1181 days


#5 posted 12-06-2019 09:39 PM


I have done it with shellac and with BLO already on. Haven’t tried with poly..

- SMP

I’m with Fred on this. I don’t think you’ll get through poly to make any color change, this is not to say the process itself may not make a change on the clock, possibly detrimental. I am not saying it will be I’m saying IDK. I do know that the strength of ammonium hydroxide solution is an extremely strong base. Ph is near 11, and anything much different than normal which is 7, can cause burns. Also burns from alkalis (base, high end of the scale) are much more severe, and always worse then with Acids (lower end of the scale) If it can cause burns it may play He(( on your poly coating.

That said, and especially if it isn’t a rush thing, get some WO, and slap a few coats of poly on it. (nobody ever does a single coat of poly) then try fuming it to see if you do get color change. A lot quicker process than stripping the entire clock, or similar. If you get the desired color change, and it doesn’t do a thing to the poly, then you could proceed to try it.

All I am certain of is this is usually done with several warnings, and never done on already finished wood. For just turning WO darker it’s now done mostly with dye, and you sure can’t dye Poly. Fuming works, but it isn’t the best method of darkening wood now, but that is just talking about the wood, as in bare wood.

-- Think safe, be safe

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pintodeluxe

6035 posts in 3420 days


#6 posted 12-06-2019 10:33 PM


I think you mean “fuming,” not “fumigating.” Fumigating is what you do if the wood has bugs, like powder post beetles. That being said, I believe the finish will prevent the fumes from reaching the oak. The oak has to be fully exposed to the ammonia fumes and a polyurethane finish (or any finish like shellac) will prevent the tannin from reacting with the fumes. Sorry, but stripping the finish is the only possibility if you want to darken the oak with ammonia. That being said, you could try putting an additional finish with coloring, such as a tinted polyurethane, over the existing finish.

- ddockstader

agree with all of this.
Glazing with a darker gel stain is also an option. Then add another topcoat.
General Finishes makes some nice products. I like their Antique Walnut gel stain.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

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SMP

1596 posts in 512 days


#7 posted 12-07-2019 01:40 AM



Yes, fuming. How were your results with shellac already on?

- Greg

I actually like BLO best. It turns a brown color vs the weird green you get fuming raw wood. Shellac seemed to take a lot longer. I used a 1lb cut garnet and came out nice but took several days(i think 4), using big box store super safe ammonia. Supposedly ACE sells 10%, but i haven’t gotten to trying it.

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Greg

40 posts in 3299 days


#8 posted 12-07-2019 02:41 AM

Thanks all for the responses. I’m going to poly a white oak scrap wood and try to fume it. I’ll reply with the results. Like I said before, I was surprised how for the darker color penetrated on the raw wood.

-- Greg - For the benefit and enjoyment of the people

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SMP

1596 posts in 512 days


#9 posted 12-07-2019 04:12 AM



Thanks all for the responses. I’m going to poly a white oak scrap wood and try to fume it. I’ll reply with the results. Like I said before, I was surprised how for the darker color penetrated on the raw wood.

- Greg

I was surprised when i fumed some 3/4 QSWO a few days, and when I cut through it, it basically had penetrated all the way through. I also remember reading a story about some bank that got remodeled, with oak moldings and crown molding, window moldings etc, after everything was all done the banker said that he had wanted all the moldings darker when came to see it. Somebody had the idea to seal up the bank with jars of ammonia, and when they came in the next day it was all the color the banker wanted. I’m guessing back then it was oil or varnish.

Curious what your results will be with poly.

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