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Bending a back strap of Black limba on a hot iron at 230 deg C using a SS bending strap.
The wood was wet with SS II and on the side with the strap I was a bit taken a when I found a strong black stain.
It sanded out fortunately, but I've not seen this before.
Took a photo of the strap, forget to take one of the wood....
This just wiped off the strap with a paper towel.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

You weren't going for ebonized limba?
I get little red dots on my stuff sometimes. Crazy. They sand out too.

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Why be normal?

why so hot you only need 275F

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Have you bent sides before when they were still wet with SS II?

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

No, first time.
The side against the aluminium bending iron was unmarked. so I must have been a reaction between the stainless steel strap and the SS.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I've noticed that pigments in wood can be mobilized by SS II when the SS II is still wet on the wood. Could the stain be pigment from a dark section of the black limba that migrated under heat?

I haven't tried bending sides when they were still wet with SS II. I let them dry first. So I don't know if that can be a problem or not. I do know that pigments were mobilized in all the colored woods I've used SS II on. When I spray bindings with SS II, color runs out of the wood onto the newspaper I lay the bindings on for spraying. When I spray sides, I leave them overnight between paper towels under a weight and I remove the paper towels in the morning. For colored woods, the paper towels are always colored from pigment that came out of the wood while it was still wet.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

As I said, no stain on the wood against the hot (aluminium) iron, only on the strap side.
I've also seen colour leached out of the wood - e.g. EIR, Zircote, etc.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Oxalic acid in a saturated solution (at least 5% oxalic acid by weight) for iron stain removal may save you some sanding time. Oak and other higher-tannin timbers are more prone to iron-staining, so your limba might fit into that category as well. Neutralize the oxalic acid with distilled water wipes or a distilled water/household ammonia or distilled water/baking soda wipe.

The oxalic acid treatment converts a visible form of the product of the ferric iron-tannic acid reaction to a colorless form. If I recall correctly, the Forest Products Laboratory has a paper on this topic, and covers a bit more of the chemistry.

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For the times they are a changin'

- Bob Dylan