Help: dark finish for red oak... - Page 3 - Woodworking Talk - Woodworkers Forum
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post #41 of 48 Old 02-16-2012, 03:01 PM
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So, I've been working on the bench and have tried the fuming again on a few samples. Here's a pic of two different tries. The one on the left was coated with the saturated tannic acid solution and fumed for around 3.5 days. The one on the right had no solution applied, fumed for around 4 days. Then, I put one layer of poly on each, leaving an uncovered "control" section in the middle without poly.

It's sorta hard to tell from the pic, but the darker one (w/ solution) has much more of a contrast between the different dark/light areas of the grain. It doesn't look "right," because the "lignin"(?) didn't soak up any of the solution, I think. I'm wondering if there is a way to give it a more uniform brown color across all parts of the wood?

The lighter sample, on the right, is satisfactorily uniform, but it's too yellow/light. I may try fuming the wood even longer - like a week. Maybe that will darken/brown it more. But, I'm assuming there's a point where all the tannic acid has been reacted with, and it won't get any darker?

I just applied a little gel stain to one section of these samples and some danish oil to another section, and it seems like the danish oil might help... darkens the areas that didn't soak up the tannic acid solution on the darker sample, and generally darkens the untreated, lighter sample. But there's still some unevenness because the lignin doesn't even like to be penetrated by the oil finishes!

Thanks
If you had 26-28% ammonia it would take less time and darken more, hard to do with weak ammonia.

Next test - dissolve the TA in alcohol - saturated solution, add 5% shellac, [zinnser sealcoat] apply with a stiff bristle brush, wipe it with a circular motion to get it down into the cell wall areas, let dry over night, the nfume it. the shellac will be so thin it will allow it to do 2 things, cling to the cell walls and allow the fumes to penetrate the rest. get back with results and pics please, outside oth that its looking good.
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post #42 of 48 Old 02-17-2012, 01:42 AM Thread Starter
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Hey Chemmy,

Thanks again for all the help.

Actually though, my lack of patience (or maybe the excitment of actually fininshing a project!) got the best of me and I went ahead and fumed my bench with no TA solution whatsoever.

But, I did some new things to help darken the results, and it seemed to help a lot:

1. Use more ammonia. Instead of one small dish, I used one large dish plus two small ones. Clearly created a lot more stink.

2. Aim some heat toward the fuming tent with a space heater. I read that a warmer temp could possibly result in a darker brown, and make the reaction happen faster.

3. Replace the ammonia with fresh stuff half way through the 4-day fuming process.

The result was a nice grayish chocolate color, which my wife actually really liked (more than the reddish brown achieved with the TA.)

Now there is a new problem (which I actually asked about in a new thread) - is there a finish that WON'T darken the fumed wood!? I know, I'm a flip-flopper, but we both like this grayish chocolate color and the wipe-on poly REALLY darkens it a lot (I tested.) Not sure what would deliver the protection needed for a table, without penetrating and darkening... water-based poly?

Thanks again!
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post #43 of 48 Old 02-17-2012, 03:54 AM
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it seems you will now need a little oxalic acid to lighten it back again.....
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post #44 of 48 Old 02-17-2012, 12:34 PM Thread Starter
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I mean, it's not that big of a deal, really.

If there is no such thing as a protective coat that can preserve this grayish/chocolaty look, the dark brown will be okay.

I was just curious...

Thanks!
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post #45 of 48 Old 02-17-2012, 02:29 PM
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Waterbased poly will darken only a little and will protect well. Waterbased vinyl will make it look exactly like it does now. Protection is a little less.
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post #46 of 48 Old 02-17-2012, 03:10 PM
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Originally Posted by mofo83 View Post
Hey Chemmy,

Thanks again for all the help.

Actually though, my lack of patience (or maybe the excitment of actually fininshing a project!) got the best of me and I went ahead and fumed my bench with no TA solution whatsoever.

But, I did some new things to help darken the results, and it seemed to help a lot:

1. Use more ammonia. Instead of one small dish, I used one large dish plus two small ones. Clearly created a lot more stink.

2. Aim some heat toward the fuming tent with a space heater. I read that a warmer temp could possibly result in a darker brown, and make the reaction happen faster.

3. Replace the ammonia with fresh stuff half way through the 4-day fuming process.

The result was a nice grayish chocolate color, which my wife actually really liked (more than the reddish brown achieved with the TA.)

Now there is a new problem (which I actually asked about in a new thread) - is there a finish that WON'T darken the fumed wood!? I know, I'm a flip-flopper, but we both like this grayish chocolate color and the wipe-on poly REALLY darkens it a lot (I tested.) Not sure what would deliver the protection needed for a table, without penetrating and darkening... water-based poly?

Thanks again!
I should have told you heating the ammonia up would quicken the process, in fact you can use a can of Sterno or gelled alcohol as a heater - make a wood square about twice the size of your dish or whatever sink 43 nails at an angle that will support the ammonia bowl, make as many as wanted! then fill your bowls with ammonia half way and first light the gel and while holding your breath, place the bowls on the nails then close up the tent. keep a close eye on the work !!!

No, there is no coating that will not darken the look to one degree or the other. I've wanted that possibility many times in my career especially with driftwood, lol. about the closest I've come is with waxes of my own making, but that would be scarce/ negligable protection for a dining table top.
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post #47 of 48 Old 02-17-2012, 03:59 PM
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Chemmy, would a very dilute application of oxalic acid do the trick for him????

thanks me friend
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post #48 of 48 Old 02-17-2012, 06:16 PM
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Chemmy, would a very dilute application of oxalic acid do the trick for him????

thanks me friend
Hi Carlo, The use of oxalic acid for bleaching uniformly is difficult, though it has a some bleaching action for sure i prefer to use it only when doing antiques or old furniture where uniformity is not so big an issue.

It's main use is as a chelating agent for the removal of metallic salts mostly iron stains [grey/ black stains] it is able to pick up and hold on to the ferric ions thus eliminating them. as a chelate it is able to grab onto metal ions to form what is know as a "chelating ring", [ a structured compound forming co-ordinate bonds that contain the metal ions] When dry it is washed off and neutralized and the piece has no more of those types of stains, though it may have other types, lol. Iron-gall inks will be removed by it also. Indian inks - NO! for India inks you would need fuming grade picric acid [dangerous stuff!!], or concentrated bleaching powder, [a mixture of calcium chloride, calcium hydroxide, and calcium hypochorite] when this is reacted with a 1-1 mixture of hydrochloric acid, by use of a pointed glass stirring rod, directly on the ink stain will remove most others.

I know for what ever reason your fond of oxalic, but personally i use it very little, though for sure it is a necessary bullet in the wood finishers gun. lol
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