Bending Blackwood---black stain

[jayluthier]

what is happening? Bending with blanket & fox bender...tried wrapping in paper...massive black stains--looks like burnt wood but it's not. Then tried wrapping in foil-- same result...then tried with no wrap..still getting massive mineral deposits...happens only with koa and blackwood (both acacia)..only comes off by sanding. How can I avoid this? seems to be worse on the side nearest the steel slat ie. not the side touching the blanket. Help!

[Bob Connor]

It sometimes imparts a greenish tinge too.

Sounds like you are wetting the wood a bit too much.

I bent some blackwood sides last week with no staining at all. I just give it a light spray with water. Say, 3 squirts of a finely misted hand sprayer on each side.

Blackwood bends pretty easily. I've done it without wetting the wood at all and just wrapping it in butchers paper.
_________________
Bob, Geelong
_______________________________________

If Becks are a sponsor next year I guess we'll just have to give East Augusta a miss.

[graham mcdonald]

It is the tannin in the wood. The steam dissolves it and brings it to the surface. Hopefully it will sand away

cheers
_________________
Graham McDonald
www.mcdonaldstrings.com

[Allen]

I'm with Bob on this. Blackwood is a dream to bend. Needs very little water. Wrap with paper, (I use the brown paper that StuMac uses to fill the box up with) then foil. And like the others said, it sands off relatively easily.
_________________
Allen R. McFarlen

[jayluthier]

Thanks for the quick response. I found the sanding would remove the stain..was hoping for a more benign solution...so, I will carefully sand. Bit of a bummer though, my dad found me a 1 metre long 8/4 vertical grain board at the timber merchant in Norwood, SA. Put it in a pea sack, plastered it with stamps and sent it to me in Washington via Australia Post. I had been waiting 10 years to use some of this wood so was sorry I had to take the aggressive approach to remove the stain. I've got 4 sets from the board, am thinking of pairing it with an Australian Cedar (toona) top based on advice from Alan McFarlane.
thanks again.
I built my first guitar in the garage of our (then) house in Hampton, Vic. 1980. Time flies!
Jay

[Allen]

The very first time I bend Blackwwod, I used light bulbs in my bender. Lots of water and galvanised metal slats. No wrapping of any kind.

It was only the second guitar I had ever made so was totally devastated when the sides came out so black and green they had no semblance of anything you'd want to use even as packing material.

They sanded up fine, but it was a lot of work. Now it's rare that I need to sand anymore than what is required on any other type of wood.
_________________
Allen R. McFarlen

[kiwigeo]

jayluthier wrote:
my dad found me a 1 metre long 8/4 vertical grain board at the timber merchant in Norwood, SA.



Not Ottos? You wont find anything like that there these days. Last time I was in there they had a few twisted tops on the shelves and nobody at the counter seemed interested in giving intelligent answers to my queries as to where all the tonewood was....the stuff they advertise every omtn in the back of one of the Australian Woodworking magazines.
_________________
One can never have enough tonewood

[jayluthier]

Yep, it was Otto. My memory cells weren't working when i sent the earlier post. Used to be a great place for wood. I'm still using the Tasmanian Oak and Jarrah workbench that I built in Burnside and moved it to Sydney, later back to Connecticut and then, finally, to Washington state. All the wood came from Otto.

[Adrian Cooper]

Posted: Fri May 28, 2010 7:22 pm Post subject:
Hi .
Have you tried oxallic or diluted batery acid.
I know that if you have used the tannin & ferrous sulphate ,or rust ,method to dye wood black ,or grey , then any acid with a pH factor below 7 will bleach the wood back to it's original color. A lot of the wood cleaners that you can buy for cleaning up exposed & oxidised raw timber thats gone grey ( such as decking cleaner )contain oxallic acid & some bleach. You can buy the oxallic acid from the chemist. It comes in crystal form.
The first guitar I made was out of blackwood. It was fairly light in tone & I bent the sides over a pipe using a fair amount of water & they ended up with a green tinge. I wiped them with a dillute solution of oxalic & that tinge dissapeared in a very short amount of time.I dont think I bothered untill after the thing was made & binding done . If I remember rightly the colors that the blackwood had to begin with ,intensified after a while too.
If the staining comes from minerals etc from the water we are using , I beleive that I once read that the water that collects in our dehumidifiers is pretty clean & could be a better source.
It could be worth experimenting a little.
_________________
" its never too late to be what you might have been" - George Eliot

[Allen]

Thanks for the info Adrian. I've got lots of water out of my dehumidifier. Enough to water the garden durning the dry season actually.
_________________
Allen R. McFarlen

[jayluthier]

Great suggestion Adrian. I was hoping for a possible less destructive fix.

I successfully sanded the inside of the box. but once it's fully asembled, I'll give the oxalic acid approach a try.
My first blackwood guitar (circa 1996) used only light bulb in the fox bender, no paper, just slats. Got a bit green, but not as black as this stuff. Different piece of wood, very different behaviour.

thanks again,
Jay

[Adrian Cooper]

Looking at my above post .Rust isn't the same as ferrous sulphate. I shouldn,t post when I'm tired. I do believe the use of acid to remove tannin stains & oxalic to clean up old oxidised wood to be correct . I know it works to reverse the green tinge too.
_________________
" its never too late to be what you might have been" - George Eliot