Black spots inside leather

[Hydrangeaceae]

I recently got some untreated veg tan, half a shoulder, and I've used about half of it without issue. 

Last night though, I noticed a lot of black spots appeared after skiving. Today I cased a piece, and now there's black spots on the surface as well. Heres some pictures. Sorry about using imgur,  I can't get pictures to work on mobile. 

Does anyone know what's going on here? I'm  afraid it's mold, but I was told it had just come in from the tannery before it was shipped to me, and I've stored it wrapped in a bedsheet in a dry room. Theres no other signs of decay/mold either. 

[Northmount]

Tannin used in the tanning process, plus iron, makes blue / black spots.  (Check out the vinegaroon process used to produce black leather without using actual dyes.)  Looks like there may be some contamination with iron filings, maybe from one of the tannery's cutting or finishing machines.  Dampening the leather will likely make the spots larger. 

In your own shop and work areas, try to make sure that no iron filings get transferred to your veg tan leather.

Tom

 

[Hydrangeaceae]

Thanks for the reply @northmount. I'm a bit confused on how iron would make spots that seem to stem from the inside of the leather though, as the spots are much larger and more pronounced on the inside layers. 

[NVLeatherWorx]

All in how the cell structure absorbs the product.  This leather was obviously tanned in a foreign tannery (Mexico, South America) as our tanneries here (and the finer European ones) pay very close attention to the equipment used and their blades are of finer metals as well.  Not bashing on anyone, just is a fact of the tanning trade and goes along way towards being able to understand what the overall term of quality truly means.

My bet is that there were indeed some iron shavings that most likely fleshed off one of the many mega-skivers and ended up collecting in the larger fat cells that were left open during the tanning process.  Nothing wrong with the leather but it can't be used for anything that will remain either Natural in color or of a lighter finish; darker colors that are applied to be solid is the best result here.

[nrk]

10 minutes ago, NVLeatherWorx said:

All in how the cell structure absorbs the product.  This leather was obviously tanned in a foreign tannery (Mexico, South America) as our tanneries here (and the finer European ones) pay very close attention to the equipment used and their blades are of finer metals as well.  Not bashing on anyone, just is a fact of the tanning trade and goes along way towards being able to understand what the overall term of quality truly means.

My bet is that there were indeed some iron shavings that most likely fleshed off one of the many mega-skivers and ended up collecting in the larger fat cells that were left open during the tanning process.  Nothing wrong with the leather but it can't be used for anything that will remain either Natural in color or of a lighter finish; darker colors that are applied to be solid is the best result here.

actually not true.

have seen same on HO leather ordered in the past(not sure about grade, but anyway)..

[Hydrangeaceae]

Thank you for the extensive reply! Assuming it doesn't suddenly grow hair, I'm really glad it isn't mold. Obviously I'm not pleased with the spots, but it was only a small piece to try out a supplier.

At least it can serve as a final push to spend more on higher quality leather. 

[NVLeatherWorx]

You would know if it was mold because you would be able to smell it; very, very musty smell for mold and it gets worse when you case it.

[YinTx]

Not sure from the photos, but that kind of looks like pores going completely through the leather....take a close look at it through a magnifying glass if you have one.  I've skived leather before and exposed the pores, or what I presumed to be pores, that looked very similar to this, and on name brand leathers.  I have not seen it on both sides though, so I'm curious if the holes go all the way through...  what do you see when you dye the leather?

YinTx

[Hydrangeaceae]

They're definitely not holes. They're too small to feel if there's any texture difference, but there's definitely no dips. Unfortunately I've just run out of dye, but I didn't notice anything weird when I dyed a large piece a few weeks ago. But then there also wasn't any spots when I skived that. 

[Hydrangeaceae]

Quick update. I just got a call from the supplier and they also believe its due to iron particles. I had unfortunately written them stating it was mold after a shoemaker looked at it, before the reassuring replies here. But I'm getting my money back, and a return label so I can return the remaining leather for them to look at. Gotta love great customer service. They're one of the only three suppliers in my country so knowing they handle issues so well, and that they are still worth ordering from, is great.