iLeatherz
Innovation and Leather
Extraction of Natural Dyes for a Sustainable Leather Dyeing Approach
Introduction
Leather dyeing is one of the most important steps of the leather making process. It determines whether the buyer would be interested in investing as aesthetic is a serious determiner in this industry.
However dyeing chemicals are known for their harmful impacts as well. Organizations throughout the world has marked several chemicals especially arylamines for their harmful properties including their carcinogenic effects. They are known for causing bladder cancer, skin irritation etc.
Another harmful constituent is heavy metal that is used on the dye making process such as metal complex dyes using Chromium as the central element for the dye. In this article a more sustainable and easily accessible elements will be used with the simplest of extraction methods.
Approach
Flower petals will mainly the used for extracting the dyes which will later on be used for the leather dyeing process. Two methods can be used one of them being using water to boil the flower petals and the other being using solvents (water or ethanol) to and then evaporating in a rotary evaporator.
Chemicals and Apparatus
- Beaker
- Magnetic stirrer with hot plate
- Filter paper
- Water bath evaporator
- Distilled Water
- Solvents (Methanol, Ethanol etc.)
- Rotary Evaporator
Extraction Methods
Water Extraction Method
- First collect flower petals or leaves from the available tree. Here we used Lagerstroemia speciosa as it was literally visible from the laboratory window.
- After that the petals were cleaned of any dirt or any other unnecessary things with water and dried. The dried petals were weighed and crushed in a mortar pestle for easy processing.
- Distilled water was added into the sample according to 1:10 ratio. And put into a stirrer with hot plate at 40-50° C for about an hour and left for cooling.
- The solution was then filtered using a filter paper and after filtering it was ready for use. The leather has to be treated with 1% solution of sodium bicarbonate and sodium formate in the drum for 30 minutes. A mordant should be used for better results however we skipped that portion.
Solvent Extraction Method
- For the second method we used the same sample as before. Took the petals washed them, dried then and finally weigh them.
- Instead of water we used ethanol for this process, added in 1:50 ratio (50mL solvent for 1g of petals) and put into the stirrer for 60 minutes at 40-50° C.
- The solution was then filtered and put into a conical flash for evaporating.
- The flask was attached with the evaporator and left for about 2-3 hours for separating the solvent that could be reused and the dye extract was left in the flask.
- The dye extract was collected. The leather has to be treated with 1% solution of sodium bicarbonate and sodium formate in the drum for 30 minutes. And as before the use of mordant is preferred.
Yield
The dye yield was calculated for flower petals.
If some one wants, they can dry the solution in an oven until it turns solid which can be crushed into powders just like our traditional mass-produced dyes.