LOGWOOD

GENERALITIES

Logwood tree (Haematoxylon campechianum) is a high tree reaching 10 to 15 meters with reddish trunk and thorny branches.

Haematoxylon campechianum

Logwood tree grows in Campeche Bay (Mexico) that’s why it is also known under the name « Campeche Wood ».
This wood has a great commercial value and as far back as the XVIIth century, large plantations of Logwood spread all over Central and South America.
For industrial purposes, only the central part of the trunk is suitable.

HISTORY

The tinctorial property of Logwood was known from the first millenium by aboriginals of Central America, the Aztecs, who were calling it « quamochitl ».
After the invasion of Central America by Spain, Europe started to use this dyewood in huge quantities, replacing the domestic vegetable dyes - woad and indigo.
As a matter of fact, this provoked a recession in the English conventional dye market leading to various wars between England and Spain in Latin America to control the Logwood harvests.
During the XVIIIth century, 95 % of silk, cotton, wool and leather black dyeing was made with Logwood extract.
Two centuries later, in 1950, world consumption of Campeche wood was still of 70,000 tons in spite of hugh competition from synthetic dyes.
Now, S.C.R-D. is the leader manufacturer of vegetable dyes including Logwood, continuing the tradition of « Compagnie Française des Extraits - Maison Westphalen » which was the initiator and the main manufacturer of Logwood through its sister companies in Jamaica/West Indies, Mexico and the United States.

COMPOSITION

The active dye of Campeche wood is Hematoxyline, discovered in 1810 by Chevreul, a French Chemist, and it belongs to the group of neoflavanoids.

Hematoxyline - or Hematine - gives by itself a blue to violet shade depending on the pH. Logwood also contains glucoside derivatives and 20 to 40 % of tan depending on the brand and the oxidation rate.

PROPERTIES

New developments in chemistry have given to tinctorial extracts a second life, freeing their elaboration from empiricism and permitting adaptation of their production to the requirements of modern leather technology.
Nowadays, tanners have at their disposal two families of Hematine :
1) Unmodified « reactive » Hematine
2) Chemically modified Hematine

UNMODIFIED HEMATINE

This colouring matter is the original dye which has been manufacturing for hundred years. Depending on the degree of oxidation, this sort of dye could be used as a penetrating or surface dye. The more the oxidation, the deeper the action. Unmodified Hematine is a latent dye - ie while most artificial dyes permit to obtain deep and immediate colouration, these special tinctorial extracts without further oxidation or addition of « striker » (metallic salts such as iron, copper, titanum, aluminium, ...) remain dull.
For this reason, it is used today only to give special surface effect to leather such as burnish and glazed.
Unmodified Hematine has high proportion of tan and glucose and it is sensitive to oxidation. By heating with glaze or fini-flex machine, it produces to a smooth, shiny and homogeneous grain, very suitable for articles like box calf, glazed kid and burnish cow.
Another advantage of using reactive Hematine is the possibility, depending on the metallic salt used, to obtain different tones with only one dye (cf. attached chart).
We could note here that Hematine combined with metallic salts reaches high fastness properties as follows :

Light	5	Levelling	5
Perspiration	5	Dry rubbing	5
Washing	5	Dry damp	4

This kind of Hematine is also highly suitable for « hair on » skin, cotton, silk and fabrics.

MODIFIED HEMATINE

New development now makes possible to use Hematine dye without metallic salt, giving a fair black shade.
These qualities are less sensitive to striker and oxidation.
Main utilisation is to permit through and through penetration without adjuvent like ammonia. Hematine also has some tanning properties and then because of self-fixation the use of formic acid is reduced.
Calf skin, buffalo and heavy bovine could be dyed with Hematine avoiding long running time.
As the proportion of chemicals entering in the modification of Logwood is not more than 20 %, the dye remains « ECO » what means ecological and economical.
Even if less than unmodified Hematine, glazing and burnishing properties are upgraded with this particular natural dye.

COMMERCIAL BRANDS

UNMODIFIED HEMATINE

HEMATINE CPMK
Natural wood dye extracted from Logwood, not oxidised, with high tan content. Mainly interesting for glazed kid, glazed calf (box calf), burnish article and combined with salts such as aluminium, iron, copper for suede stain since washing fastness becomes excellent.
This dye can be used in finishing mixture.

HEMATINE CFMK
Same than CPMK but fully oxidised. Black shade is stronger, but penetration and tanning power are less. Compared to CPMK, grain will be flatter because the oxidation has provoked a reduction of tan astringency. Suitable for glazed, burnish and multi-tone effect when combined with metallic salts. It can be used in finishing mixtures.

HEMATINE HS
Semi-oxidized Hematine without astringency. Properties are between those of Hematine CPMK and Hematine CFMK.

HEMATINE LBH
Natural extract, pure of extraction, oxidised to Hemateine and specially formulated for nylon dyeing and pharmaceutical suture threads.

 

MODIFIED HEMATINE

VEGDYE NS
Non oxidised Hematine modified to avoid the use of mordant such as iron and copper. Its high penetrative power makes it suitable for fast through-dyeing for economical process. It could be used as an alternative to Nigrosine or Sulphur dye types.

VEGDYE NO
Same than Vegdye NS but based only on oxidised Hematine. Suitable for glazed kid and glazed calf. Vegdye NO could be used in finishing mixtures.

VEGDYE BMS
Hematine modified to obtain a marine blue dye. It has the same physical properties than Vegdye NO but with a different shade.