Bleaching mold stains

[Captain Eddie]

I have a really nice bowl, turned green, but sat in wet shavings too long. I have some mildew stains on it. Simple bleaching idea is needed. Input would be appreciated. It's maple with some ambrosia.

 

[Jim Rutten]

Hi Captain,

I was in a class with Bobby Clemons last year and he had some badly mildewed wood (I think it was sycamore). He took a lemon and sliced it into quarters and rubbed it on the mildew and then let it dry. He had to do this two to three times, but at the end you couldn't even see the mildew. Good luck.

Jim

 

[Steve Worcester]

You can bleach it with the standard 2 part from Home Depot but it will alter the unmildewed portions too.

 

[bfwhitma]

Oxalix acid

I am right now waiting to see the results of my oxalic acid solution on a gray mildew stain in maple--oxalic sold in boxed powder form like pumice and rottenstone. The lemon slices appeal to me!

 

[Mark Mandell]

I am right now waiting to see the results of my oxalic acid solution on a gray mildew stain in maple--oxalic sold in boxed powder form like pumice and rottenstone. The lemon slices appeal to me!

Oxalic will remove iron stains and brighten sun-darkend woods (major ingredient in deck wash products) but it won't do much for penetrated mold stains.

I use small portions of the 2-part wood bleach. Mix and then add water to dilute by 50%, then apply to the spots with a moistened paper towel.

WEAR GLOVES!

You'll have more control with the paper towel or a very small brush. If working on a bowl, remember that the stuff can wick through the end grain and drip into the interior to spoil the color. Therefore apply lightly and be prepared to blot off.

 

[Odie]

I have a spalted maple bowl that was roughed about two months ago......I've been very excited about this bowl, because it's one of the most beautiful spalts I've ever had. It's Maple. I just yesterday noticed that it's getting some mildew darkening. I just about had a heart attack when I saw this........!

This pic was taken just shortly after it was roughed, and wax coating applied for drying. (The wax isn't completely dry yet.)

I've never attempted to remove mildew before, but do you think I can use the lemon trick on this wood? If it gets on the spalt, will it alter that?

Should I wait until it's weight stabilizes and use the lemon just prior to finishing it.......or, would it be best to take a little slice off the exterior now.....do the lemon.....and re-wax for drying.

???????

Thanks for your input on this......

otis of cologne

 

[Ed Koenig]

Trisodium phosphate (TSP) is sold at any big box store an will remove mold. TSP may be used with chlorine bleach to remove mildew from wood. TSP alone can cause dark stains on redwood and chlorine bleach prevents it.

TSP is a very strong cleaner at the dilutions normally used, which vary from 1/2 cup TSP to 2 gal. warm water for "heavy duty cleaning" to 1 cup TSP to 3 quarts warm water for "ridiculously heavy duty cleaning" (source The Savogran Company). For mildew killing, household bleach is added to the TSP/water mixture. The recommended ratio is 1 part household bleach to 4 parts water.

Read the manufacturer's mixing ratios, as they may vary.

Ed

 

[Odie]

Trisodium phosphate (TSP) is sold at any big box store an will remove mold. TSP may be used with chlorine bleach to remove mildew from wood. TSP alone can cause dark stains on redwood and chlorine bleach prevents it.

TSP is a very strong cleaner at the dilutions normally used, which vary from 1/2 cup TSP to 2 gal. warm water for "heavy duty cleaning" to 1 cup TSP to 3 quarts warm water for "ridiculously heavy duty cleaning" (source The Savogran Company). For mildew killing, household bleach is added to the TSP/water mixture. The recommended ratio is 1 part household bleach to 4 parts water.

Read the manufacturer's mixing ratios, as they may vary.

Ed

Hey, thanks for this information Ed.......

I was sort of hoping to hear from someone who has used lemon to remove mildew, because it sounds so easy to do. That's still a possibility, I suppose, but I would like to hear from someone with hands on experience with it.

Judging from the woods you use, I'd say you are a good source of information for what works on mold and mildew.....and thanks for the input. I'm sure I'm not the only one who stands to learn something about this from this thread.

I have a question for you on this........What would be the best way to deal with mold on the bowl blank in the picture? Should I deal with this now, or wait until the bowl blank has moisture content stabilized, and ready for final turning?

What would be the best way to apply the TSP/bleach solution? Any special procedures you would recommend?

Your input on this is appreciated, Ed.

otis of cologne

 

[MichaelMouse]

Black mildew is a real PITA, especially on light-colored woods. Best advice is to get as much unbound water out as possible to help it through the FSP to ~18% MC point where mildew won't grow. If you spin fast, you'll throw a lot of it onto the tablesaw.😱 If you blast air you'll get more out. Don't coat it to hold moisture if you have reasonable RH, and don't bother to coat the inside of a bowl, where the mechanics of compression as the piece dries will close any incipient checks. Works to your benefit, since you'll have the least material to turn away on the inside end grain.


NB: Most "TSP" sold today at big box stores isn't. Seems the P part is great fertilizer, and if you wash it down the drain it will fertilize algal blooms. That's why it's banned. We didn't have enough sense to spray the waste on the lawn or garden. Real TSP is some powerful stuff, ranking just below lye. Laundry detergents used to be 0.5 per cent TSP and the rest fillers and fragrances. Spic and Span was 1.5 per cent, as memory serves

 

[Ed Koenig]

Hey, thanks for this information Ed.......

I was sort of hoping to hear from someone who has used lemon to remove mildew, because it sounds so easy to do. That's still a possibility, I suppose, but I would like to hear from someone with hands on experience with it.

Judging from the woods you use, I'd say you are a good source of information for what works on mold and mildew.....and thanks for the input. I'm sure I'm not the only one who stands to learn something about this from this thread.

I have a question for you on this........What would be the best way to deal with mold on the bowl blank in the picture? Should I deal with this now, or wait until the bowl blank has moisture content stabilized, and ready for final turning?

What would be the best way to apply the TSP/bleach solution? Any special procedures you would recommend?

Your input on this is appreciated, Ed.

otis of cologne

Otis,
I mainly use TSP/clorine to kill mold and mildew which grows in shady areas on my deck and house. It works great for my application. I have limited experience using it on bowls so your best bet is testing it yourself. I've only used it on non spalted turning wood that was solid. I've always applied it sparingly just to be on the cautious side. Better safe than sorry. Good luck.
Ed

 

[Odie]

Otis,
I mainly use TSP/clorine to kill mold and mildew which grows in shady areas on my deck and house. It works great for my application. I have limited experience using it on bowls so your best bet is testing it yourself. I've only used it on non spalted turning wood that was solid. I've always applied it sparingly just to be on the cautious side. Better safe than sorry. Good luck.
Ed

Ok, thanks Ed........I understand.

I'm sorta forming a plan of action here......into the unknown!

I think what I'll do is mount the bowl and take a very thin shaving off the darkening area to see if it is only on the surface. If so, I can remove all of it by doing this. If not, I'm first going to try the lemon trick.

If neither of those two things are successful, I'll get some TSP and do some testing with that.

Still would like to hear from someone who has used either method on a bowl blank before...........preferably spalted wood.

otis of cologne

 

[Odie]

Update:

I had another bowl that had some mold developing, so I decided to try out the lemon trick on it to see what happens.

I had to remount the bowl (I think it's Magnolia), and take off a layer of wood on the exterior to remove the wax coating.

I bought both a fresh lemon, and a little bottle of lemon juice.....applied some of each to the molding. After a day, I could see a definite lightening of the mold area. The lemon juice works better than the fresh lemon, but both work. I'm not sure how well it's going to work, because it's obvious that it'll need repeated applications to lighten the mold appreciably. The surrounding wood also lightened some, so the conclusion is that the entire bowl surface will need an application of lemon for the effect to look right.

The Magnolia bowl began to crack after a day, so I had no choice but to take off another layer of wood and rewax for drying.

I conclude from all this, that it might be best to wait until the roughed bowl has stabilized and ready for completion before the lemon treatment can be used effectively.

Any comments about this?

I'm posting a pic of the Magnolia bowl used in this lemon experiment, plus a pic of the spalted maple bowl just after roughing, and a few months later. You can see the growth of the mold clearly in the second pic......on the left side.

At this point, I haven't done any TSP testing yet.

otis of cologne

 

[George Van Beynen]

I get the mold under the Anchorseal at times when I wax the green roughed piece before the surface area is dry(I now usually wait overnight to let the roughs start to dry before sealing). I have had many get a light layer of black mold under the wax but by turning to 10% of the diameter rough thickness I have not had problems removing the stain well before the finished thickness has been reached. If this bowl is a couple of months old and the mold was bothering me I would mount between centers and clean up the blank then reseal after the mold is removed. You should still have plenty of thickness left to allow for continued warping while it is final drying. Good Luck, George

 

[Odie]

I get the mold under the Anchorseal at times when I wax the green roughed piece before the surface area is dry(I now usually wait overnight to let the roughs start to dry before sealing). I have had many get a light layer of black mold under the wax but by turning to 10% of the diameter rough thickness I have not had problems removing the stain well before the finished thickness has been reached. If this bowl is a couple of months old and the mold was bothering me I would mount between centers and clean up the blank then reseal after the mold is removed. You should still have plenty of thickness left to allow for continued warping while it is final drying. Good Luck, George

Thanks for that input, George.....

I'd have thought there would be lots of input on this thread, but it hasn't turned out that way.

I will try waiting overnight as you suggest. That could backfire with some bowls, because I've had roughed bowls start cracking in less than a day's time after roughing.

otis of cologne

 

[MichaelMouse]

I will try waiting overnight as you suggest. That could backfire with some bowls, because I've had roughed bowls start cracking in less than a day's time after roughing.

otis of cologne

If you're a fan of broad-bottom thick-wall styles as you've shown in this thread, you'll want to be extra careful of your drying speed. Try the advice further above of blowing unbound water out with compressed air and/or centrifugal force, and reduce your open air time to that required for a dry-appearing surface on the outer endgrain.

It also looks as if you're waxing the interior of your bowls, something which is unnecessary, since any incipient cracks have compressive mechanical stress working to close them. Out on the endgrain where there is tension rather than compression is where you want the coat, if you coat. I have a high-humidity basement in the summer, and a garage where the temperature, when not below freezing, is pretty close most of the rest of the year, so that's where I store fresh roughed blanks. Take your humidity gage on a road trip and see if you can't find a nice place for stepping yours down.

 

[George Van Beynen]

Thanks for that input, George.....

I will try waiting overnight as you suggest. That could backfire with some bowls, because I've had roughed bowls start cracking in less than a day's time after roughing.

otis of cologne

I may have suggested something that may cause you a problem in YOUR area Otis. The relative humidity in your shop may be drier than mine (40% avg.)and cause your wood to dry faster which could cause problems if the roughed bowls were left exposed for 12 hours overnight. Maybe if you still have a problem tyr to find an area of high humidity as Michael suggests or let them rest in a paper bag till morning. I also use my method on maple, birch, and yellow birch, I would worry about cherry and other fruit woods. I am sure you have access to other woods in your area than I do in northern Wisconsin.
I learned from Michael years ago to place the waxed roughs on the floor of my basement to start as they dry a lot slower initially, then when the weight loss slows (as measured on a scale) I move to higher shelves or the pole building where they are stored till needed.

 

[Odie]

OK, thanks George.....

I can see I'm going to have to adjust the way I do things......for the roughed bowls of very high moisture content.

One thing that kind of confusing to me is MM's suggestion to not wax the interior of the bowl for drying. Although I have always waxed both inside and outside of roughed bowls, it seems like bowls that aren't waxed on the inside will still dry out too fast. Wouldn't water find the path of least resistance here? Seems like it would, anyway.

One bit of good news here is I took a layer off the spalted maple bowl and eliminated the mold altogether.....!

I rewaxed it immediately. (It's been drying for a couple of months now, so I figured it's dry enough that the mold won't restart.)

otis of cologne

 

[MichaelMouse]

One thing that kind of confusing to me is MM's suggestion to not wax the interior of the bowl for drying. Although I have always waxed both inside and outside of roughed bowls, it seems like bowls that aren't waxed on the inside will still dry out too fast. Wouldn't water find the path of least resistance here? Seems like it would, anyway.

They do lose moisture through the inside at a faster rate, but since the wood is under compression due to geometry, checks will not open, but squeeze closed. Look at your dried heart up bowl and notice that it's has squeezed narrow and the sides have dropped. Both put compressive stress on the inside.

Which is why it's the odd work indeed which splits inside out.

 

[Raul McCai]

WOW. I came to this thread hoping to solve exactly the problems referenced here .
I've a huge crotch I've been working on. It 'was mostly dry when I got it ( mostly).

After roughing It's been stashed in a room in a bag in a box to dry some more.
Yesterday as I was working it I saw appreciable dark black clouds of mold. I didn't like 'em.

I may re-sand and go at it with chlorine I have some 12% but first I'll try lemon juice

Chemically I can't imagine why TSP would have any effect on color. It's use in cleaning is as a surfactant.

I would not have defaulted to chlorine without reading this thread because Oxalic acid is the go to wood bleach but fact is I want to address the mold cloud not the wood.

I may end up with some anyway.

This guy trued Bher's Deck Cleaner he says is oxalic acid
http://forums.finewoodworking.com/fwn-experts/pgedrys-not-taking-questions/cleaning-white-oak
Claims it was working well and then after a soda wash ( to neutralize I suppose) it got worse.
Maybe if he'd water washed it ?
He's using Taunton's guide to finishing. I just bought a copy from Abe Books for $6.00



Here is an author Bob Rice from University of Maine
http://www.esf.edu/nekda/documents/SomeThoughtsaboutStainanddiscolorationinWood-BobRice.pdf
He doesn't reccommend TSP

He speaks to a slew of acids and compounds
Citric acid
Phosphoric
Hydrochloric
Disodium Peroxycarbonate ( deck Brightener)
Chlorine




I already own some chlorine 12% for my pool. I have bottles of pure Citric acid crystals, I have some oxalic acid in Bar Keeper's friend (brand) cleanser

I've read that a soak in Denatured Alcohol may kill ( stop) the mold. ( Seems a pretty bit tank of alcohol would be needed)
I imagine that wrapping in black plastic and leaving in the hot summer sun for a few days might do it if it gets over 150F.



I think I'll start with a lemon.
I take some pics and get back

 

[Owen Lowe]

WOW. I've a huge crotch I've been working on. It 'was mostly dry when I got it ( mostly).

Nobody likes a braggart, Raul. (I’ll leave the second joke ^ to someone else!)

I think I'll start with a lemon.
I take some pics and get back

I wonder why a heavy spritz of just good, old, diluted Clorox (maybe 1/2 cup to a quart of water) wouldn’t be just the ticket? Seems like it gets rid of a lot of over-steamed, no-fan-running, 20-minute-teenager-shower-causing black bathroom spots in our house.

If it’s a roughout (I can’t really tell from the original post) it’ll mostly be turned away anyway after drying. If it’s a once-turned bowl, Clorox it and see how it goes. Maybe Clorox and direct sunlight.

 

[Raul McCai]

Nice.
Very dry.


Well I tried citric acid
I tried Oxalic acid

A wipe with chlorine seemed to do the trick

From this
http://i1002.photobucket.com/albums/af143/zydaco/The Shop/PM lathe/dark oxalic -02_zpsdfaoma2r.jpg

To this
http://i1002.photobucket.com/albums/af143/zydaco/The Shop/PM lathe/20150625_191352_zpsyoreq8l7.jpg

 

[Zach LaPerriere]

a professional approach to killing mold (but not removing stains)

It's worthwhile to go back a few years in the American Woodturner, where Sara Robinson recommends that you can kill any mold on wood with a spray bottle of 10% bleach (90% water) and another spray bottle of 91% or 99% rubbing alcohol (bought at that concentration from the drugstore.) Spray both on the mold.

"Spalted Wood, Health and Safety," 26.4: page 50

and here's the link for the article, if you click on Aug 2011, 26-4. You have to be signed in to your AAW account:
http://www.woodturner.org/?page=aw2010s

Sara Robinson is assistant professor at the Applied Mycology Lab, Oregon State University. Great article!

I just tried this, but I can report back here soon. Anyone else using the bleach and alcohol spray bottles?

 

[Richard Coers]

It's worthwhile to go back a few years in the American Woodturner, where Sara Robinson recommends that you can kill any mold on wood with a spray bottle of 10% bleach (90% water) and another spray bottle of 91% or 99% rubbing alcohol (bought at that concentration from the drugstore.) Spray both on the mold.

"Spalted Wood, Health and Safety," 26.4: page 50

and here's the link for the article, if you click on Aug 2011, 26-4. You have to be signed in to your AAW account:
http://www.woodturner.org/?page=aw2010s

Sara Robinson is assistant professor at the Applied Mycology Lab, Oregon State University. Great article!

I just tried this, but I can report back here soon. Anyone else using the bleach and alcohol spray bottles?

Curious wording in your first sentence, since this post started over 7 years ago, on 02-22-2008!