Overview
This week was a time for some small experimentation with gels.
We were looking at agar and gellan gums. Several things were of interest to us as a group and so we divided up the labor and testing amongst ourselves.
One group looking into making gels with laponite gel, which is usually used in painting conservation but which we had not tried in our previous lectures on gels.
Another group looked into xanthan gel, a soft gel which we had not used before.
One group looked into the difference in the preparation of the gels: to see if the resulting gels differed depending on it they were made on a hot plate or in the microwave.
Personal Project
My teammate and I worked on creating a loaded agar and gellan gum for the use of hypertonic and bleaching uses. In order to make a hypertonic gel, we added salt to our gels so that the ion content would increase the movement of ions between the gel and the paper.
For the bleaching gel, the goal was to create a gel that could be used to bleach in local areas of the paper. For this, we used hydrogen peroxide as the bleaching medium.
Two methods of creating loaded gels were attempted. One was to create a normal agar or gellan gum and to then let them sit and immerse in a bottle of either the salt or hydrogen peroxide solutions. The second attempt was to integrate the solution into the gum as they were being created.
Gel Samples Created
We came up with a total of 10 gels to test on sheets of 18th-century paper.
The following were immersed gels; gels which were created using our usual recipe for agar and gellan gum and then left to soak in the solutions:
A 5% Gellan Gum immersed in a 2% salt solution
A 2% Gellan Gum immersed in a 2% salt solution
A 5% Gellan Gum immersed in a 1.4% hydrogen peroxide solution
A 2% Gellan Gum immersed in a 1.4% hydrogen peroxide solution
A 2% Agar Gel immersed in a 2% salt solution
A 4% Agar Gel immersed in a 2% salt solution
A 2% Agar Gel immersed in a 1.4% hydrogen peroxide solution
A 4% Agar Gel immersed in a 1.4% hydrogen peroxide solution
The last two gels were gallan gums which we added the solutions to while creating the gels:
A 2% Gellan Gum created with a 1% salt solution
A 2% Gellan Gum created with a 1.4% hydrogen peroxide solution
Note: My teammate and I did not create the agar gels we used here. The ones used here were given to us by our classmate which had looked into the difference between hot-plate and microwave made gels. All the samples of Agar were created on the hot plate with the exception of number 6, the 4% in a salt solution, which was made in the microwave.
RECIPES
1.4% Hydrogen Peroxide Bleach
Note: the reason this is a weird 1.4% is because our starting bottle of hydrogen peroxide was at 35% and this was easier to measure.
4ml hydrogen peroxide
96ml water
2% Salt Solution
1g salt
49ml water
shake and stir until the salt is dissolved
Gellan Gum (2% and 5%)
2 or 5g gellan gum
98 or 95ml water
(normally you would also try to add some calcium acetate, 0.04, but the tap water in Amsterdam is high in calcium so we skipped this)
Mix gum into the aqueous solution
bring to a boil
pour out on a tray and let cool
2% Gellan Gum with a 2% salt solution
2g gellan gum
44ml water
Optional 0.04g calcium acetate if you don't live in Amsterdam or if you are using DI water
0.5g salt
Mix gum into the aqueous solution
bring to a boil (for the salt mixes we let the gel reach about 80℃)
pour out on tray and let cool
Note: the salt causes the gel to become less transparent
Agar Gel (2% and 4%)
2 or 4g agar
98 or 96ml water
mix together
heat to boiling for about 30-60 seconds
pour and let cool
2% Gellan Gum with 1.4% Hydrogen Peroxide Bleach
1g gellan gum
48ml water
Optional 0.04g calcium acetate if you don't live in Amsterdam or are using DI water
2ml hydrogen peroxide
Mix gum into the aqueous solution
bring to a boil
Just as the gel is ready, add the hydrogen peroxide, then pour out on a tray and let cool
Results and Concluding Thoughts
We used sheets of 18th-century hammer beaten paper for the tests. One sheet was used for the salt solutions, one sheet was used for the hydrogen peroxide.
We had left the gels overnight and in the morning added the ammonia (about 5 drops per 50ml) to activate it. We waited about 10 minutes after activating the solution before placing the gels on the paper. The bleaching gels were left on for one hour before removing them.
For the salt solution gels, we left the gels on the paper for 10 minutes before removing them to see the effect on the paper.
Notes on the hydrogen peroxide:
The gels were just placed on the paper without weights which I think caused the infused gel to not have an even result in bleaching. If someone were to use it for local bleaching I would suggest using weights.
Notes on the salt solutions:
Overall the salt does not seem to matter much regarding the swelling of the paper. There is not much difference between the control group and the gellan gums. The agar gels are generally wetter and so there seems to be more swelling in the areas where agar gels were used.
If this were a more serious experiment which would later be published, we would have gone ahead with attempting agar gels with the solutions integrated in during the creation process. Since this was a quick two-day experiment, we decided to cut some corners.
Sources:
Velzen, Bas van. Class presentations and handouts on gels and bleach recipes, 2019-2020.
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