07-31-2006, 02:48 AM
Okay, my basic tests are done. Bear in mind these are qualititative, not quantitative. No measurements were made and the different materials simply compared to one another.
Materials and Methods:
I used average-strength hide glue (315g), mixed 1:2 glue:water, heated to about 70C. The rawhide was unbleached and about 1mm thick (dry). I don't know what type of hide it was, except that it wasn't pig. The leather was chrome or alum-tanned pigskin lining about 1.5oz, about 0.6mm thick when saturated and dry. The wood substrate was birch (scutum leftover) 3mm thick and 3.5cm wide.
The leather was soaked in the hot glue for 10 minutes and agitated to ensure it became saturated. One section of rawhide was soaked in warm water for 1 hour and then blotted lightly. The dry rawhide and birch substrate were sanded lightly with 200 grit sandpaper to roughen them slightly. Glue was applied to both the wood and various material patches to ensure a continuous bond. A piece of plastic was then applied on top and then a second piece of birch plus some clamps to ensure all was held tight until the glue gelled. After 15 minutes, the clamps, wood and plastic were removed to allow all to dry. One corner of the wet rawhide patch was accidently lifted but the remainder was considered sufficient to permit testing. After 24 hours the wet rawhide patch was found to have been lost during some accidental movement of the wood. A previous piece applied to 1/8" plywood 24 hours previously (total drying time 48 hours), however, was intact and substituted for this qualititaive test.
The birch strip was tested by bending it along its length with the experimenter's thumbs (that is, me
) immediately behind the centerpoint of the patch of each material. The qualitative, relative force (as it appeared) necessary to crack the wood and tear or separate the material was then judged as more or less than the others and they were ranked strongest to weakest. A further test of plain wood was then conducted as a control.
Results:
Strength
1) All materials appeared to increase the force necessary to break the wood considerably. Neither the dry rawhide nor the soaked leather separated from the substrate before tearing, and both tore only as the wood broke- apparently partly at least because of the splintered wood edge. Unfortunately, the wet rawhide substitute piece might not have been entirely dry as ultimately wasn't terribly hard to tear with my bare fingers.
2) The dry rawhide was stronger than the glue-soaked leather, but not as much as might have been expected given that the former was about twice the thickness.
Glue Performance
1) hide glue will bond wet rawhide, but it's quite easy to accidently lift sections and thus spoil the bond. The glue gels when it cools down, not when it dries, but only solidifies when it dries- so the glue remians a gel as long as the rawhide is wet. Since the wet rawhide is so flexible, it's VERY easy to separate it from the glue for a day or more I should think. After 48 hours, as already stated, it wasn't 100% dry either.
Conclusions
Well, technically, I can't really say anything for sure since the wet rawhide test wasn't properly completed. I see some difficulties with working with rawhide has a number of problems. Having worked with hide glue a fair bit now, I can say that it wouldn't be easy to use it to secure a pice of dry rawhide to a scutum face. For large areas, it's usually necessary, because the glue gels fairly quickly, to work in sections- difficult to do with a semi-rigid material as you cannot fold it easily without accidently pulling up already glued areas. That would suggest that wet rawhide would be the thing to use, however it has its own problems. As already stated, it's very easy to separate the hide from the glue even after the latter has gelled. Also, rawhide contracts when it dries and I do wonder if that might be part of the reason it wasn't as strong as the dry rawhide- something I hope to find with the repeat test.
Applying glue-soaked tanned leather would be easy enough if very messy. Thoroughly saturating such a large piece of leather could be problematic- a large container and a lot of glue would be necessary, and a specialized setup to heat it. Luckily, hide glue can always be turned to gel again with water and heat, so it's not hard to clean up.
Here are pictures- the top is the dry rawhide, the bottom is glue-soaked tanned leather:
Materials and Methods:
I used average-strength hide glue (315g), mixed 1:2 glue:water, heated to about 70C. The rawhide was unbleached and about 1mm thick (dry). I don't know what type of hide it was, except that it wasn't pig. The leather was chrome or alum-tanned pigskin lining about 1.5oz, about 0.6mm thick when saturated and dry. The wood substrate was birch (scutum leftover) 3mm thick and 3.5cm wide.
The leather was soaked in the hot glue for 10 minutes and agitated to ensure it became saturated. One section of rawhide was soaked in warm water for 1 hour and then blotted lightly. The dry rawhide and birch substrate were sanded lightly with 200 grit sandpaper to roughen them slightly. Glue was applied to both the wood and various material patches to ensure a continuous bond. A piece of plastic was then applied on top and then a second piece of birch plus some clamps to ensure all was held tight until the glue gelled. After 15 minutes, the clamps, wood and plastic were removed to allow all to dry. One corner of the wet rawhide patch was accidently lifted but the remainder was considered sufficient to permit testing. After 24 hours the wet rawhide patch was found to have been lost during some accidental movement of the wood. A previous piece applied to 1/8" plywood 24 hours previously (total drying time 48 hours), however, was intact and substituted for this qualititaive test.
The birch strip was tested by bending it along its length with the experimenter's thumbs (that is, me
) immediately behind the centerpoint of the patch of each material. The qualitative, relative force (as it appeared) necessary to crack the wood and tear or separate the material was then judged as more or less than the others and they were ranked strongest to weakest. A further test of plain wood was then conducted as a control.Results:
Strength
1) All materials appeared to increase the force necessary to break the wood considerably. Neither the dry rawhide nor the soaked leather separated from the substrate before tearing, and both tore only as the wood broke- apparently partly at least because of the splintered wood edge. Unfortunately, the wet rawhide substitute piece might not have been entirely dry as ultimately wasn't terribly hard to tear with my bare fingers.
2) The dry rawhide was stronger than the glue-soaked leather, but not as much as might have been expected given that the former was about twice the thickness.
Glue Performance
1) hide glue will bond wet rawhide, but it's quite easy to accidently lift sections and thus spoil the bond. The glue gels when it cools down, not when it dries, but only solidifies when it dries- so the glue remians a gel as long as the rawhide is wet. Since the wet rawhide is so flexible, it's VERY easy to separate it from the glue for a day or more I should think. After 48 hours, as already stated, it wasn't 100% dry either.
Conclusions
Well, technically, I can't really say anything for sure since the wet rawhide test wasn't properly completed. I see some difficulties with working with rawhide has a number of problems. Having worked with hide glue a fair bit now, I can say that it wouldn't be easy to use it to secure a pice of dry rawhide to a scutum face. For large areas, it's usually necessary, because the glue gels fairly quickly, to work in sections- difficult to do with a semi-rigid material as you cannot fold it easily without accidently pulling up already glued areas. That would suggest that wet rawhide would be the thing to use, however it has its own problems. As already stated, it's very easy to separate the hide from the glue even after the latter has gelled. Also, rawhide contracts when it dries and I do wonder if that might be part of the reason it wasn't as strong as the dry rawhide- something I hope to find with the repeat test.
Applying glue-soaked tanned leather would be easy enough if very messy. Thoroughly saturating such a large piece of leather could be problematic- a large container and a lot of glue would be necessary, and a specialized setup to heat it. Luckily, hide glue can always be turned to gel again with water and heat, so it's not hard to clean up.
Here are pictures- the top is the dry rawhide, the bottom is glue-soaked tanned leather:
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