How to Dye Leather Black

[Shorts]

Interpret:

In experimenting the last day or two, dropping in a swatch of veg tanned hide into a base solution of baking soda and water produces no visible chemical reaction.

Dropping a swatch of dyed with vinegar and water solution into a rinse of baking soda/water produces no visible chemical reaction.

Dropping a swatch dyed in vinegar into a rinse of baking soda and water produces a very visibly active chemical reaction.

[Leerwerker]

Here are some answers I got from the leather chemists when I asked them about this method of coloring leather:

1.

The black color is the reaction of Ferric salts or oxide with tannings, nice formula for leather crafts, but it is a pain in the neck in vegetable tannery.

2.

First: this is not a dye is an iron (ferric) salt.

Second: The leather may be damaged by the excess of acid: white vinegar is acetic acid and if applied in excess can give some problem according to what was stated in the post. Iron react with vegetable tannins giving a product that is black.

Neutralizing the leather is not wrong. In the industrial process this is also being used even though the term is confusing because it does not mean to take the leather up to the neutral pH condition or the 7.0 value. It means to neutralize some of the acid inside the leather to avoid acid damage. The final pH for vegetable leather can be around 4.0 and this is far from neutral.

3.

The process is sometimes used to make black leather through a process called striking. In fact, I believe there is a commerical product called Striker.

David used the process commercially back in Colombia. I still have the black leather hat that he gave me from this type of leather.

4.

You are right, I also used them in Colombia in order to save some money on dyes,on heavy veg retannage we used ferrous sulphate to create a nice black color all thru the cut replacing the expensive colored veg extracts "unitones". Other strikers used were copper sulphate, ferric chloride and titanium potasium oxalate ( for brown shades) an adittional advantage was the capacity of strykers to mordent the dyes uniform on veg retan or veg leather making a little better "coverage" if the word is correct of the defects as scratches, at least they were less evident. Limitation obviously was the necessity of veg extracts to create the complete system.

SO, it seems the best pH for leather is 4 - quite acid!

Hope this helps!

JOhan

[Shorts]

Thanks Johan, good info. (My use of the word "dye" was not in reference to the black solution)

My idea on my above observations was that the acceptable level of acidity in leather alone was not going to be reduced by putting it in a baking soda bath. Is that a relatively safe statement for the intensive purposes here?

[Leerwerker]

Thanks Johan, good info. (My use of the word "dye" was not in reference to the black solution)

LOL - When I put the word dye in 'dye' quotes, the one chemist guy did not see the tongue in cheek quotes! Of course I know it's not real dye, but he had to point that out to me!

My idea on my above observations was that the acceptable level of acidity in leather alone was not going to be reduced by putting it in a baking soda bath. Is that a relatively safe statement for the intensive purposes here?

I would want to caution on the side of acidity, but I must also admit that even my college chemistry is now getting to be more that three decades old ....!

[sodapop]

i guess what i would like to know since some of it went over my head...

all in all is this a safe method for the leather??

and if i understand it right...

1st dip in the dyeing mixture

2nd essentually rinse/neutralize in the baking soda solution

3rd let dry then apply oil etc??

is it after you apply the oil that brings out the black basically??

thanks

darryl

[Shorts]

Here's an example of my solution and product. I put the wool into the vinegar on the 31st, so its been curing for 2 days. I dipped a strip of veg tanned leather in and left it for a minute or two, then pulled it back out, rinsed with cool water and there it is. No transfer of color when I rubbed it on the white papertowel. I'll get a pic of the strip when it is dried for continuity. But as you can see, wet, it is very dark black (looks like I dipped it in black ink).

After it dries, I'll take a pic both dry and with oil.

Edited April 2, 2008 by Shorts

[tonyc1]

Here's an example of my solution and product. I put the wool into the vinegar on the 31st, so its been curing for 2 days. I dipped a strip of veg tanned leather in and left it for a minute or two, then pulled it back out, rinsed with cool water and there it is. No transfer of color when I rubbed it on the white papertowel. I'll get a pic of the strip when it is dried for continuity. But as you can see, wet, it is very dark black (looks like I dipped it in black ink).

After it dries, I'll take a pic both dry and with oil.

What sort of wool?

[Duke]

I believe it would be steel wool.correct me if im wrong

[Shorts]

What sort of wool?

Steel wool

[tonyc1]

Steel wool

Oh, They get that from hydraulic rams don't they???

Couldn't resist it!!!