Official Luthiers Forum!

Hey gang -
I rencently purchased a bending blanket and spring steel slats, switching over from bulbs. After two uses, I'm hooked on the blanket BUT I'm getting wierd black/blue spots. Not scorches, they're stains...and they're only on the bottoms, where the spring steel touches the kraft-paper wrapped wood.

The sandwich = slat, wrapped wood (wetted), blanket, slat. The spots are happening where the wrapped wood contacts the steel. The paper absorbs MOST of whatever the stain is, but the wood gets some of it too. I know nothing of gunsmithing or metal in general, but the slats look as if they were "blued"...and whaddya know, the spots are that color as well.

Should I have cleaned the slats with some kind of solvent before first use? They looked nice and clean, no residue that I could feel.

I use spring steel .. the blue looking stuff, and discovered early on that the wood needs to be wrapped in foil .. that keeps the moisture in as well ....

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

Try putting a barrier layer of aluminum foil between the spring steel slat and the craft paper wrapped wood.

I use stainless slats and craft paper with no issues and I also run a third slat, spring steel on top of the blanket but not in contact with the wood.

So my stack looks like this from bottom to top:

1) Stainless slat
2) Wood lightly spritzed with distilled water wrapped in craft paper
3) Stainless slat
4) Blanket
5) Spring steel slat

Note that my blanket does not come into contact with the wrapped wood either, it sandwiched between two stainless slates.

I hope this helps - it sounds to me like the spring steel slats are the source of the blue stains.

Thanks for the quick replies! Yup, sounds like the simple fix is to add a layer of foil between the bottom slat and the wrapped wood.

May be a dumb question, but what exactly is craft paper and where do you purchase it

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John Ressler

Craft paper = brown paper for shipping packages. Walmart, Kmart, etc.

You can also use parchment paper which is in your grocery store with the baking stuff. It's used for making cookies and keeps them from sticking to the tray. Translucent White and not too expensive.
Comes on a roll like tinfoil. I like tinfoil too.

Taylor uses the kraft type paper, mainly to cut down on oily resin transfer between sets. The papers also act like absorbent sheets and remove resin from woods like Indian and Cocobolo rosewoods.

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http://www.dickeyguitars.com

Here's one more solution. Buy a can of black paint used to paint barbeque grills. It's high temp paint.
I sand the blued steel then spray. Also prevents the stell from rusting when wet. Rusts before your eyes.
Renew every 6 months or so depending on how often you bend.

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Hi all:

Help me out here - what does a slat on top of the heating blanket contribute to the bend if there are two other slats on either side of the wood? I am only on instrument #8 so have much to learn. Thanks.

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GEO
perpetual beginner

Adds support to the sandwich and helps hold in the heat of the blanket. If the blanket is exposed on the top the on about 50% it heat efficiency is being used if a slat is add to the top this increases to about 70-75%. this interns means less wattage to achieve the same radiant heat.

Thanks. I will give it a try today on some European Maple.

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GEO
perpetual beginner

George welcome to the OLF!

In addition to what my pal Michael said regarding the use of a 3rd slat - some of us prefer to not have the blanket in direct contact with the wood. I use a 3rd slat for this reason as well as belaying the heat loss from the top of the blanket.

I also use a 3rd hold-down caul on my Fox style bender to hold the outer most part of the lower bout firmly on the bending form.

Thanks for the welcome and the useful information. Local master builder Dake Traphagen told me yesterday that we never stop learning about guitar building and he has been at it for 35 years. I just want to live long enough to get halfway good at this.

I do use two slats and parchment paper on either side of the wood and the blanket on top. With a third slat on top of the blanket do I have to recalibrate the time on the bending form? By this I mean adjusting time and temp for the additional heat? I use a controller (from Blues Creek) but with my limited experience there is still a big element guesswork involved in getting a good bend and not overheating the wood. As is said, there is no such thing as a failed experiment. Each teaches us something even if it means toasting some Australian Blackwood.

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GEO
perpetual beginner

Wrap your wood in aluminum foil and you will no longer have stain problems. No need for anything else.

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Sylvan
http://www.wellsguitars.com