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Iron Mordents

This page is designed to give a better understanding of what color should be obtained when using the iron mordents to produce black.  One would think that black just means black but there can be many shades.  When leather is dyed black it falls into two color ranges, dark green and deep blue.  When iron mordents are used correctly it falls into a dark blue range.  Careful dyeing techniques must be used to overcome the blue to make a good black color.

Note:  Lamp Black is not discussed here because it is mostly used on the flesh side of leather.

The following pictures are to give you an idea what the iron mordent looks like when used properly and improperly.   This type of dyeing when done right leaves a deep black.  The best description I have heard of the color is called telephone black.   The old time telephones had a deep dark black.  Dyeing leather the correct black is one of the hardest things in the production process. 

When iron mordents are used to dye leather black the tannins in the leather form a chemical reaction with the iron mordents.  As the iron mordents change form from FE1 to FE2 a deep black color is achieved.  When done properly this should be a black that will last for as long as the leather exist.
 

Warnings about dyeing with the iron mordents.

“When an insufficient amount of logwood infusion is applied to the leather previous to the application of the iron solution, the latter will combine with the tannin in the leather and render it inert, thus acting destructively upon the leather causing it, subsequently, to become brittle and tender.  It is, therefore, of the utmost importance, when staining or dyeing logwood-iron blacks, that a sufficiency of logwood should be applied to the leather for the iron to combine with, so that there may be no liability of the oxidizing action of the iron salts taking place at the expense of the tannin in the leather.[1]

In staining blacks it is very necessary that plenty of the logwood infusion should be applied to the leather, especially if this is at all lightly tanned.  Unless there is plenty of tannin and coloring matter to unite with the iron, the iron will combine with what there is of tannin matter in the leather, and render it brittle and liable to crack.    If too much iron is used, the leather may be completely ruined.  The writer has seen many cases where the leather has been rendered brittle by too little logwood and too much iron.[2] 

Just where did the dye formula in the 1861 ordnance manual come from?   In a series of letters in the archives we can put together the whole story behind this formula.  

In a letter dated November 15, 1852 from Thornton, New York Arsenal, to Craig, we find the original formula.

From/To:  Thornton, New York Arsenal, to Craig)

I have the honor to acknowledge the receipt of your instructions of the 8th inst and in answer to give the following information respecting a Dye for blacking buff leather. (Materials in the following proportions)

Take 5 ounces of the Extract of Logwood

4   "    of Pulverized Nutgall &

3   "    "  Copperas

Enclose the Nutgall and copperas in a coarse bag, and put it with the extract of logwood and a quart of rain water in a vessel over a moderate fire, so that it may boil slowly until the copperas is entirely disolved (sic-dissolved) then remove the vessel from the fire and let it stand undisturbed until the liquid has settled and become cold, after which decant it into bottles and the die (sic-dye) is ready for use.  If the colour is found too blue add copperas, but on the contrary if too black add the extract of logwood.

To blacken buff leather, apply the die with a sponge or soft brush and when the application has become dry, brush the leather gently with a clean stiff shoe or cloth brush. 

There is a whole set of letters going back and forth until the confusion over the chemicals.  In this letter copperas is used instead of Pyroligneous acid, but before the right name for the acid is found it is suggested that “oxyde of Iron” may be the chemcal used to produce the black.  The letters go back and forth until the exact name of the chemical is detremined as can be seen in this letter from

  From/To:  H.A. Dingee, New York, to Craig

 Your communication of the 27th Inst. I this day received; and in reply have to say that the "Oxyde of Iron" which I use in blacking Buff Leather, or Belts is a "Liquid" made from Pyroligneous acid, with as much Iron as it will take.

As directed I have also written to Major Hagner relative to the above, stating that if he should find it difficult to procure the acid, or make the Liquid, I should be happy to send him, a carboy containing any quantity he may require of the Solution, ready for use.

                As can be seen from the letters there was quite a lot of confusion over black dyes and the chemicals that went into them.   This seems not to have been corrected even in the 1862 Ordnance manual. 

To see more pictures how they dyed leather during the 19th century.

This original box shows the beautiful black obtained during the 1860's.

The center strap has been dyed correctly and the color is black not brown as the other two straps.

Here an original belt shows the great differences between the colors obtained.

The background is a piece of leather that has been properly dyed with iron mordent and finished by jacking.  The two straps are a comparison of incorrectly dyed leather.  Tanners of the 1860's made an art of their dyeing techniques. 

 We have worked very hard in the last few years to make this change in our production process.  When "period dye" leather is advertised by sure to look for the correct color if you are looking for a truly authentic item.  Generally, if the correct deep black color is not achieved it is not of the correct ph level.  If the correct ph levels are not met it can cause irreparable damage to your leather, i.e. acid rot, case hardening etc.

These straps illustrate just two of the incorrect shades that can be obtained using the "period dye" with iron mordents. 

Again, be sure to look for the deep black color when buying your gear.

Just how Did the tanners of the time dye and finish leather? 

The information below is a period quote to show how they really dyed and finished leather.

The first clue to just how this beautiful black was dyed comes from Campbell Morfit’s book under the section on currying sleeked leather.  “The leather is now blackened while still upon the table, being moistened before this operation, if it has become too dry, since a certain degree of humidity is necessary to enable it to receive the color.  For this purpose, a mop of wool, or brush of horse-hair, is dipped in the composition prepared for the purpose, and the hair side is thoroughly rubbed with it in every direction.   Two applications of black are generally required for sleeked leather, and when any parts of the surface remain of a red color, even a third may be requisite.  When the leather is of a fine black color and perfectly dry, it is exposed to the action of a press for a time not longer than two weeks, during which it is increased in density and firmness, the excess of tallow being forced out from it

In order to give the last dressing to these skins, the hair side is well wiped, so as to remove any portions of grease remaining upon it or mould which has formed on the surface.  A polish is given with sour beer or barberry juice, and the surface is slicked with a very smooth stretching iron or a lump of smooth glass.[3]

 “exposed to the action of a press for a time” this is a four post press with a upper and lower plate that could be tightened by a hand screw, or the leather was piled and blanks weighted down with rocks was put on top of the pile.

 What has just been explained in detail is how leather was dyed and finished for items such as cartridge boxes, cap pouches, scabbards, and parts of tack used in horse equipment.  This leather had a fine surface that had good luster or shine.  This leather was not as highly polished as patent but would have had a good shine.  This point is further illustrated in the same section on currying sleeked leather, when it is described on how to clean up the bad spots.  “If any spot of grease or defects of surface remain, the parts which are thus deficient are gently rubbed with a cloth dipped in polishing liquid, until they become perfectly bright.”[4]

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