October 14, 2006

Dermal Ridges, Flexion Creases and Casting Artifacts, Part 5

*Photo's by Chris Buntenbah, Wildlife Photographer*

This will be my final post on this issue, until I have the actual soil from Onion Mountain (I hear sometime in July :) ) I got a little off track and did not post the final casting test.

This test was done differently.

Casting Cement: Plaster of Paris (mixed thick)

Water: Heated to 80 degrees (in an attempt to duplicate conditions at casting site, and to see if I could force expansion)

Substrate: Tricalcium Phosphate heated to 80 degrees ( in an attempt to duplicate conditions at casting site, and to see if I could force expansion)

I finally have artifacts. But, these artifacts are curious as they are not "Crowley Lines".

On the outside of my foot - there is a very prounounced Y-shaped crease - It's my opinion, that was caused by the casting cement, ok explanation here. When I heated the water and put in the Plaster of Paris, I instantly noticed how fast this was actually thickening up. When I poured it into the cast with my hand - there was little to no flow, I tried to push it a bit with my fingertips gently, but to do so would have ruined the area of the track. So, what you are seeing is from adding in additional Plaster of Paris above this line and to the side. I did see this very lightly with the test in 70 degree water, but not to this extent, which tells me, it has to be the heated water. Now, if I were to see that after casting a track of unknown origin, I would know it was not a flexion crease -- as flexion creases follow the natural movement of the foot - this does not.

Ok check out the picture

I did not heat my water above 80 degrees. As stated above, I tried to simulate actual conditions or a good medium - I was told it was very dry and hot that day. I do not know what the actual temperature was, or humidity. But, Im pretty sure water heated to 100 degrees was not used for the Onion Mountain cast (but I could be wrong).

So, it is possible to get dermal ridges and flexion creases using Plaster of Paris, in a substrate with the consistency and feel of ash, as I suspected.

So, are all of the dermal ridges and flexion creases in the Onion Mountain cast simply "artifacts"? I dont think we can say that -- I think they should be evaluated as Jimmy Chilcutt has done. But I have noticed the introduction of heat and moisture brings out more detail. As some of the best casts where when I heated water, heated the substrate and soaked my foot.

But, thats just my opinion. :)


  • At 10:40 PM, Blogger Melissa Hovey said…

    Thank you Steph :) I didnt realize how much work actually goes into casting until I started doing this work. I actually enjoy it - and I hope we can all learn together.

    Stay tuned, as there will be new casting experiments soon. And, the results may surprise you.


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