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Yesterday I started bending the myrtlewood sides for a guitar I'm working on. The regular non cutaway side bent beautifully. A perfect bend, no springback, no staining, no problems whatsoever. I wrapped it in wet brown craft paper and sandwiched it between two stainless steel slats with the blanket on top.
The cutaway side did not go so good. It's got some fractures so I'm not going to try to use it. The only differences are that I bent between to spring steel slats since it is a cutaway, and I wrapped the wood in foil instead of paper. I think the wood must have dried out in the foil being the reason it cracked. I have done plenty of successful cutaway test bends when wrapping in paper and then re-wetting during bending. The only problem is every time I do this I get some bad staining and I cant figure out why. The only way I could bend the cutaway test between spring steel without staining was to wrap it good in foil. Has anyone else here had the problem of bad staining when using spring steel? Any help would be greatly appreciated.
Here are some pics.

Stained maple test


Stained koa test


Stained myrtle test


Spring steel slats

Is it normal for spring steel to look like this after only experimenting with them a few times.

some woods could react with the spring steel, but you didn't mention whether you used distilled or tap water.
i use distilled water and alfoil to try and eliminate staining problems.

The stain is a combo of issues oils in the wood, water, ambient dust particles and a bit of galvanistic staining. I have had the same issue on some woods when using Kraft paper. I will sand off.

Yes the spring steel will oxidise from the heat just keep them clean of dust and oils from the woods and they will be fine.

Cracking, fracturing, faceting is a common issue on curly or quilted woods Especially in cutaways. this is due to the radical grain orientation change in curly and quilted figuring. The stress pulls the grain going perpendicular to the plates normal grain path apart.

I have had great success with SuperSoft II in eliminating this.

I just used tap water. I guess I should try distilled.

Michael, how do you clean your slats? Mine seem to rust extremely fast. I've been using an extra fine steel wool (0000 I think) to take it off. Do you think this could be causing any problems?

It really is not rust per say it is oxidation of common air borne contaminates, oil and minerals in the water.

(use only distilled water every where you use water!!!!!)

I just wipe them down with Naphtha after every use. I will not get rid of all the oxidation on the slat but will control it

If I am not familiar with the wood I am bending I bend in Alum. foil to help prevent the staining.

Once the bluing on your spring steel slats wears off, they will rust very quickly. Different woods will react differently on the naked steel, causing all kinds of staining problems.
I tried painting my slats with high heat engine paint. Turned out to be a bad idea... The paint softens up with the heat & gets sticky enough to transfer to adjacent surfaces.
Even if you are using stainless steel slats, I believe its important to wrap the side in foil. (I know lots of guys get away with it, but I'm too chicken to try it.) Unless the slats are spotlessly clean, you never know what reaction you'll get when you add water & heat & then leave the whole package to stew overnight.

I always wrap in foil, but for the drying cycles, I use a box knife to (carefully) slit the edge of the foil. this allows moisture to escape freely while maintaining a foil barrier between the wood & the slats.

I should mention that some woods (Koa for example) will stain in contact with aluminum foil. A wrap of parchment paper works to separate the wood from the foil. Craft paper may work as well, (& less expensively) but I haven't tried it. After replacing an expensive set of Koa sides, I'm happy to fork out the $ for parchment paper... But I'm a braces & belt kind of guy.