Introduction

The purpose of my experiment was to determine the best drying conditions to produce a fresco without cracks. To do this, I chose 4 different drying environments. The first was a warm, dry environment, the second was warm and damp, the third was cool and dry and the final was cool and damp. The other variable was cross-hatching the second layer on four of the frescoes, to determine whether or not crosshatching created a stronger bond between the second and the third layer.

I hypothesized that the best drying location would be warm and dry. I also hypothesized that crosshatching would help the third layer bond to the second layer

Procedure

1. slate lime

2. Coarse and fine sand

3. 8 wooden frames, with chicken wire on the base, 8 by 12 by 2 inches

4. Water

5. Pre made pigments

6. Paintbrushes

7. 2 lamps with 100 watt bulbs

8. Vats for mixing the sand and lime

9. Plastic tubs with lids for drying the frescoes

10. Trowel

11. Containers, i.e. baby food jars, to hold the water

1. Mix the first layer of sand and slate lime in one of the mixing vats. This layer is 2 parts coarse sand, 1 part slated lime. Using your hands, with gloves on, as the mixture is caustic, mix the sand and the lime until the mixture is consistent throughout

2. Using a trowel, place the first layer into the wooden boxes. This layer should be approximately 1/2 to 3/4 of an inch thick

3. Cross-hatch this layer before it hardens

4. After letting the first layer dry for a week, dampen the 1^st layer with a spray bottle and apply the second layer. This layer also is 2 parts coarse sand and 1 part lime.

5. Cross hatch the second layer on 4 of the 8 frescoes and allow them to dry

6. The final layer is composed of 1 part fine sand and 1 part lime. Make sure this is completely mixed before applying. Apply using the trowel. This layer should be 1/3 inch thick.

7. Paint the frescoes using the pre mixed pigments

8. For the first 2 frescoes, one crosshatched one non-crosshatched, place in a warm damp environment. This is created by placing the frescoes in a plastic tub with two containers of water. Then turn a lamp on them, with a 100-watt bulb in the lamp.

9. The second two frescoes are to be placed in a warm, dry environment. This is done by just shinning a 100-watt bulb on the frescoes. They can be left out in the open if the weather is not to damp, or placed in a plastic tub, with the lid on, if the weather is damp.

10. The third two frescoes are to be placed in a cool, damp environment. This is created by placing the frescoes in a plastic tub with to containers of water and sealing the tubs so no air can be released. Then place the tub in a cool area, out of direct sunlight.

11. The final two frescoes are to be placed in a cool, dry environment. This is accomplished by placing the frescoes in a tub, sealing the tub and placing it in a cool environment out of direct sunlight.

12. After a period of 2 days, the frescoes can be removed from their respective environments and the results of the drying can be observed.

Observations and Data

The first layer, which was comprised of 2 parts coarse sand and 1 part slated lime was very difficult to apply into the boxes. The reason for this was the layer of chicken wire that lined the bottom of the boxes. The mixture did not spread evenly in the boxes until it had hardened for a short period. This layer began to crack immediately after it had been crosshatched. The cracks appeared, in all of the frescoes, along the edges, radiating towards the center. The layer also began to pull away from the edges of the boxes. This layer was a light tan in color and was very grainy due to the sand’s coarseness.

The second layer was also comprised of 2 parts coarse sand and 1 part slated lime. This layer was also difficult to apply. After the first layer was dampened the second layer stuck to the first layer. This layer also immediately cracked, from the edges again, radiating towards the center. The frescoes began to pull away from the edges of the boxes, much more severely than they had during the first layer process. Once I crosshatched the four frescoes, crack began to appear in the crevices. But the cracks on the crosshatched frescoes were not as deep or pronounced as on the non-cross hatched frescoes. This layer was identical in color to the first layer and also had a great deal of texture.

The final layer and third layer was also applied after the second layer was dampened. This layer is comprised of 1 part fine sand and 1 part lime. This mixture was the hardest to work with. It was very glutinous and stuck to everything. This layer was the thinnest layer, approximately 1/3 to 1/2 inches thick. It was much whiter in color and had much less texture than any of the other layers. When this layer began to dry, before I applied the paint, small cracks began to appear on the frescoes, with no regard to whether or not the frescoes were crosshatched. After the paint was applied, I placed each fresco in the different environments.

Conclusions

After the frescoes have dried completely and removed from their containers, the results of the project are very clear. My hypothesis that the warm and dry frescoes would crack the least was not quite right. The warm and damp frescoes dried the best. There was almost no cracking on the frescoes. When the water evaporated the air within the container was cooler than it would have been with no water. The drying process was slowed down when the water evaporated and so less cracking occurred. The warm and dry frescoes cracked some-what, all cracks radiating from the edges. They were not enclosed in an entirely dry environment so perhaps they would have cracked more if the air was completely dry. The air in the lab was not especially damp but there was some moisture in the air. I would have gotten better results had the frescoes been completely enclosed in a dry environment. The frescoes in the cool and dry environment cracked much more than the previous two. They cracked mostly from the edges due to quicker drying time that occurred because of the dry environment. The final two frescoes, which were dried in the cool and damp environment, cracked the worst. The water did not evaporate at all in the container and the frescoes cracked immediately from the edges.

All of the frescoes pulled away from the edge of the boxes, which may have caused most of the cracks, which radiated from the edge towards the center. The crosshatching of the second layer did not make a difference in any of the frescoes. Each of the two frescoes that dried in similar environments experienced similar cracking patterns so I concluded that the crosshatching had no effect on the cracking of the frescoes.

From the Fresco Cracking Investigation sheet, I gathered that the drying process of frescoes is very difficult to generalize. Some people’s frescoes dried well when the air was damp, some cracked severely and others cracked a small bit. Each fresco is made differently and there is no way to make each one have the same depth or the same smoothness or the same concentration of sand and lime, so therefore there is no real way to determine where the cracking will occur or whether or not it will occur. The environment defiantly does play a role in how the fresco reacts, damp and warm does seem to be the best environment but it might change with how the fresco is created. My original plan to determine whether acid rain has an effect on frescoes would have been very interesting. But this project will give students in the future ideas on how to create lasting frescoes. The other part of my original plan, to test different pigments also would have been interesting, but with the project I devised, it was much more useful to use pre made pigments. Preventing cracking in frescoes is important because to make them last to their full potential, cracks must not be allowed to form.

References

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