June 20, 2011

Alum Tanning

The alum tanning process did not successfully tan the first test strip. The test strip remained cream colored and rubbery. It was unclear whether the alum tanning process did not work or if the test strip was not properly bated. The third test strip will be used to determine which process did not work.

Vegetable Tanning

The second test strip was left in the vegetable tanning solution. This piece has become deeper in color.

Dehairing

Hair was removed from the 3rd test strip.

Soaking

The third test strip was soaked in distilled water to remove the sodium hydroxide.

Baiting
6 g of pepsin were added to 600 mL of distilled water and 18 mL of acetic acid. This solution was heated to 37°C. The third test strip was placed in this solution and the hot plate's magnetic stirrer was used to stirr the solution.

June 17, 2011

Alum Tanning
Alum tanning paste was removed from the first test strip and the final layer of tanning paste was applied. This layer will be left on for 3 days.

Vegetable Tanning

The second test strip was left in the vegetable tanning solution.

Overnight the piece of hide had changed in from cream colored to burnt orange. It had also become slightly tougher and more dimensionally stable.

Liming

The third test strip was removed from the distilled water and placed in a solution of 200 mL of distilled water and 2g of sodium hydroxide to loosen the hair from the hide.

June 16, 2011

Alum Tanning

The alum tanning paste was scraped from the first test strip and a new layer was applied.

Vegetable Tanning

300 mL of distilled water was combined with 100 mL of quercitannic acid solution obtained by soaking oak bark in distilled water. The second test strip was added to this solution. I plan to gradually increase the concentration of the solution to which this strip is exposed.

Trimming

A third test strip was cut from the large hide

Soaking 

The third test strip was placed in distilled water to remove salt and blood.

June 15, 2011

Alum Tanning

The alum tanning paste was again removed from the first test strip and another layer was applied.

Baiting
The second test strip was baited again. This time, 500 mL of distilled water was mixed with 5g of pepsin and 18 mL of acetic acid (CH₃COOH) to reduce the pH of the solution. This solution was heated to 37°C. After several hours the sample was removed from the heat and observed. The fatty layer that had been on the flesh side of the test strip seemed to be mostly removed. 

June 14, 2011

Alum Tanning

Alum tanning paste was gently scraped from the fist test strip. A new layer was applied and the strip was placed back in the beaker.


Baiting

The second test strip was placed in a solution of 500 mL of distilled water and 5 g of pepsin and heated to 37°C. After several hours it became clear that the bating process was not working so I will try again tomorrow.

June 13, 2011

Pickling 

The first test strip was removed from the bating solution and placed in a solution of CH₃COOH (acetic acid) and H₂O with a pH of 4.5 to lower the pH of the hide in preparation for tanning. To create his solution 350 mL of H₂O was mixed with 15 mL of CH₃COOH. The hide remained in this solution for 2 hours. 

Alum Tanning

90 mL of H₂O, 30 g of unbleached flour, 30 g of NaCl, 30 g of KAl(SO₄)₂^.12 H₂O (Alum),  and 15 mL of egg yolk (one egg yolk) were combined to form a paste. 

This solution was applied to the test strip.


Dehairing
The second test strip was removed from liming solution and hair was removed in the same manner as was used for the first test strip.


Soaking 

The second test strip was soaked in water to stop the liming process.


Vegetable Tannins

The oak bark pieces were removed from the solution in which they were soaking. 

June 11, 2011

Baiting
The test strip in the pepsin solution was left in solution to continue digestion of unwanted proteins.

Liming

The second test strip was placed in an NaOH solution of 200 mL of H₂O and 2 g of NaOH. The solution had a pH of 10. The test strip was left in solution overnight to loosen the hair.

June 10, 2011

Dehairing

The test strip was removed from the HaOH solution and laid flat on the table. NaOH solution was disposed of in a labeled hazardous waste container.

Hair was removed from the hide by running my fingers over the hair applying light pressure. Hair was discarded.

Soaking
The test piece was soaked in distilled water to remove the NaOH. The resulting solution had a pH of 7.5 and was discarded in the same hazardous waste container as the NaOH solution.

Baiting

1g of pepsin was added to 500 mL of H₂O and heated to 37°C. Pepsin is an enzyme that digests proteins. In leather tanning, pepsin is used to dissolve unwanted proteins from the animal hide leaving behind tannable collagen in the skin.


Debarking

 
Bark was removed from oak branches with a draw knife for vegetable tanning. 

The bark pieces were placed in distilled water to removed the quercitannic acid from them. Quercitannic acid is the tannin found in oak bark with the formula C₇₆H₅₂O_46. 

The solution immediately began to turn an amber color. The pH of this solution was 6.5.

June 9, 2011

Trimming

A square approximately 9"x9" was trimmed from the large hide.

A square approximately 3"x3" was cut from the large hide for testing purposes.

Resalting
Excess wet salt was scraped from the hide.

550 g of NaCl was added to the large hide.
450 g of NaCl was added to the small hide.

Soaking
The 3"x3" test strip was placed in distilled water for 24 hours to remove blood and salt.

The solution had a pH of 7.5 when the piece of hide was removed.

Liming
An NaOH solution was made by combining 200 mL of H₂O with 2 g of NaOH. The pH of this solution was 10. The 3"x3" test piece was placed in this solution at 1:45 pm. 

Due to the high pH of the solution, the hide was checked for progress at 6:30 pm; however, the hair was still firmly attached to the hide at this time. 

June 7, 2011

Trimming

The hides were removed from the refrigerator and laid flat on the table.

Unwanted animal material such as hooves, heads, and other organs were trimmed from the hide with a hunting knife. Some unwanted muscle and fat tissue were removed from the flesh side of the hide.

Salting

1000g of NaCl was placed on the large hide to cure it. 500g of NaCl was placed on the small hide. The hides were transfered to a wooden board and tilted to drain. They were then covered with a piece of foam and left to dry and drain for two days. 

June 6, 2011

The hides were taken out of the freezer to defrost. After several hours, the hides were placed in the refrigerator to continue defrosting over night.

June 5, 2011

Two goat hides were obtained from Sudlersville Frozen Meat Locker, a butchery in Sudlersville, Maryland. Sudlersville is located approximately an hour from Newark, Delaware (where the University of Delaware is located). Goat hides were chosen for this project because their hides are thinner than those of cows and pigs and therefore tan quicker. We considered local hides to be more desirable than hides that could be obtained online because they did not have to be shipped and because the treatments done to the hides could be more easily obtained. The hides were frozen to preserve them for the weekend.

These are the hides we received from Sudlersville Frozen Meat Locker.