Tips on Working with Spalted Mango for B&S

Ken C · **Posted:** Thu Jul 08, 2010 4:26 pm

I have some nice spalted mango that I want to start turning into a small jumbo. The back panels have fairly heavy spalting, resulting in beautiful patterns but also less than stellar structural integrity. The sides have only marginal spalting and seem fairly sound. I wouldn't dare use the backs without some strengthening. I have read that some folks recommend soaking in CA or epoxy thinned with denatured alcohol. I can see how this would add strength but could make glue up with white glues a bit troublesome I would imagine. Also have thought of laminating a very thin maple veneer to the inside of the back.

Depending on the wood, I thin sides to 80 to 90 thou prior to bending on my Fox bender w/heat blanket. As the integrity of the sides seems pretty good, I presume this is still a reasonable guide.

Would appreciate any insight those of you have worked with spalted woods could share with respect to adding strength, gluing up, and bending.

Ken C

Brock Poling · **Posted:** Thu Jul 08, 2010 7:02 pm

Ken C wrote:

I have some nice spalted mango that I want to start turning into a small jumbo. The back panels have fairly heavy spalting, resulting in beautiful patterns but also less than stellar structural integrity. The sides have only marginal spalting and seem fairly sound. I wouldn't dare use the backs without some strengthening. I have read that some folks recommend soaking in CA or epoxy thinned with denatured alcohol. I can see how this would add strength but could make glue up with white glues a bit troublesome I would imagine. Also have thought of laminating a very thin maple veneer to the inside of the back.

Depending on the wood, I thin sides to 80 to 90 thou prior to bending on my Fox bender w/heat blanket. As the integrity of the sides seems pretty good, I presume this is still a reasonable guide.

Would appreciate any insight those of you have worked with spalted woods could share with respect to adding strength, gluing up, and bending.

Ken C

Depending on how soft the spots are I might just leave it a bit thicker than usual and go for it. I would be more concerned if the sides were soft and the back was solid. Bending spalted woods can be challenging.

Another thought might be double backing the back plate with nomex and an inner core (just glue it up in your dish). If it were me, I would couple it with a mahogany inner skin.

As far as joining it. I would probably use epoxy

My biggest problems working with spalted woods came in finish prep. It is really hard to not over sand the soft areas and get divots. I have used blocks, hand sanded etc. and it helps but you still have to be careful.

But the pay off is pretty spectacular. The woods are beautiful under finish.

Zach Ehley · **Posted:** Thu Jul 08, 2010 8:31 pm

No words of wisdom here, but you may want to get ahold of Tim Metcalf. This stuff looks pretty cool when wet.

see:
http://www.luthiercom.org/phpBB3/viewto ... =20&t=1960

Ken C · **Posted:** Thu Jul 08, 2010 9:22 pm

Thanks for the insight, Brock. I have some thin mahogany veneers. They are only 6” wide, but I don’t see why I couldn’t use a three piece veneer on the inside. Wonder if that would make the guitar sound more like a mahogany or a mango guitar

Guess I could also veneer the sides, but can’t believe a prelaminated piece would bend that well. Heatwise, Titebond should be okay, but with the inner and outer radiuses running different lengths, seems like trouble.

Could certainly join the panels using epoxy, but attaching the back with epoxy seems like a pain, but perhaps not.

Filippo, my understanding is that once the wood has been kiln dried, all the fungus is dead. I usually have a dust mask on when sanding anyway.

Thanks,

Ken

Daniel Minard · **Posted:** Thu Jul 08, 2010 10:51 pm

I recently finished a guitar using heavily spalted maple for the peghead overlay & the rosette. It took several coats of heated finishing epoxy to make it ready to shape, let alone ready to sand & lacquer. This stuff was like balsa wood... Probably much further gone than your pieces. Sure looked gorgeous when it was done, but what a pain!

BTW... If by "dust mask" you mean one of those inexpensive paper masks you get in the hardware store, beware. Those things are worse than useless, since they give a false sense of security & very little in the way of protection.
The paper masks with the rubber face seal are much better. A real dual filter respirator is better still.
Interesting thing I learned at an aircraft re-finishing seminar, years ago.... A workman's comp guy told us that a half day's growth of beard can reduce the effectiveness of a respirator by as much as 40%. He wouldn't even talk about using one with a full beard.

Brock Poling · **Posted:** Thu Jul 08, 2010 11:16 pm

Ken C wrote:

Thanks for the insight, Brock. I have some thin mahogany veneers. They are only 6” wide, but I don’t see why I couldn’t use a three piece veneer on the inside. Wonder if that would make the guitar sound more like a mahogany or a mango guitar

Guess I could also veneer the sides, but can’t believe a prelaminated piece would bend that well. Heatwise, Titebond should be okay, but with the inner and outer radiuses running different lengths, seems like trouble.

Could certainly join the panels using epoxy, but attaching the back with epoxy seems like a pain, but perhaps not.

Filippo, my understanding is that once the wood has been kiln dried, all the fungus is dead. I usually have a dust mask on when sanding anyway.

Thanks,

Ken

IFF you were going to laminate the sides you will want to do it after you bend them (not before). That is my standard way of doing all of my sides. I just put them on a form in a vacuum bag. It works very well. However... I would be a bit careful doing this with the spalted mango. Thinning these way down to use them for double sides might cause challenges. 1) They can get soft in spots and crack in the bends and 2) during finish sanding you can get divots and you could easily sand through. If the sides seem very solid I am sure you can do it, but just factor this into consideration.

I use epoxy all the time on funky wood and it works great. Except for the 2 minutes of mixing (and the alcohol clean up) it is actually easier to work with than white or animal glue. If you think there is any chance that the plates have any punkiness at the joint I would use epoxy. ;-)

Ken C · **Posted:** Fri Jul 09, 2010 7:46 am

I guess if I use epoxy as my adhesive of choice in dealing with the back, then I will just soak the back panels in alcohol thinned epoxy prior to working with it. That should strengthen the back considerably and won't impact how the epoxy adheres when joining, bracing, and gluing onto the rims. Brock, I think my rims are good enough to thickness to 90 thou with no problem. I'm a little nervous with how they will bend, but assuming they bend okay, I can always soak with thinned epoxy once bent to add some additional strength. Not sure if soaking with thinned epoxy prior to bending would be a good idea or not.

I don't have many dust allergies. The one wood that does give me fits is balsa. None of the others I have worked with have bothered me. I have pretty good dust collection and filtration in my shop. My dust masks are paper, but not the really cheesy paper ones with the metal tab over the nose bridge. I am sure it is not as effective as a dual respirator, but it seems to keep my nose clean, and I haven't had any adverse reactions! My Dad worked in a cabinet shop for years. No dust collection. No mask. He is 85 with no resperatory issues. Granted he wasn't working with exotic woods much, but he certainly inhaled a lot of oak, ash, popler, maple, walnut, cherry, and alder.

Ken

Barry Daniels · **Posted:** Fri Jul 09, 2010 8:22 am

And my grandfather smoked cigarettes every day until he died in his eighties. That does not mean this is safe.

Ken C · **Posted:** Fri Jul 09, 2010 8:40 am

Barry Daniels wrote:

And my grandfather smoked cigarettes every day until he died in his eighties. That does not mean this is safe.

And I am not saying I am sanding without dust collection, filters, and a mask! I appreciate everyone's concern over my health. But my thread related to strengthing, bending, and gluing spalted mango. If you all want to talk about the dangers of dust, let's start a new thread. I really don't need help avoiding dust!

Ken

Bailey · **Posted:** Fri Jul 09, 2010 10:26 am

Wow! I finished a Spalted, curly mango Om a few months ago and it was a delight to work with. Bent easily, back and sides were stable and needed no extra bracing requirements. It sounds great and looks great. I found my sets Spalted areas were not soft at all. I luckily purchased 2 sets and have another set for a future build..
Kent Bailey

Quine · **Posted:** Fri Jul 09, 2010 12:34 pm

I guess great minds think alike....I'm doing a spalted mango guitar now too. My spalting was only a single vein though. I didn't do anything special with it. It was the easiest set of sides to bend I've ever worked with.
If yours is really fragile, maybe a veneer on the inside would help stabilize it.

Bailey · **Posted:** Fri Jul 09, 2010 2:17 pm

Don't know if Minwax product Wood hardener is a possibility for dealing with pithy or soft areas. I've never used it on a guitar...only wood carvings. It went on clear and after a couple coats 2-3 hrs. between coats..dries hard and is workable and sandable with hand tools. Don't know how it would affect sides before bending either.....But I do like the product for what it does..
Might be worth a try on a scrap and also see how the dry wood then reacts to fillers/sealers and finish.
kent

Bobc · **Posted:** Fri Jul 09, 2010 4:50 pm

here's a link to some info that may help with stabilizing spalted wood.
http://www.veddermountainhardwoods.com/2009/02/27/stabilizing-techniques-for-small-pieces-of-spalted-wood/

Ken C · **Posted:** Mon Jul 12, 2010 1:51 pm

Thanks for the feedback guys. I have been out of town for a couple of days and am just getting back to this.

Bailey, nice guitar! Can you share a few details? How thick were your sides prior to bending? What sort of glue did you use? Sounds like your wood had most of its integrity still in tact.

Quine, same questions. Nice to hear this stuff is easy to bend.

Bob, thanks for the link. Good stuff.

I checked the sides again, and I can only locate one bad area along one edge of the rims. The back, though, has a fair amount of less than stellar structure. I should be able to treat it and perhaps leave it a little on the thick side and be okay. As Brock noted, I may have to use epoxy to glue join and attach it to the body.

Ken

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