This summer I plan on getting out for some bigfoot expeditions. Part of the essential gear is casting material. People always want to cast bigfoot tracks, right?
What works best? How long do I have to wait for it to dry? Does one thing work better than other stuff? I'm going to compare Plaster of Paris, Hydrocal, and DAP Patch N' Paint.
Plaster of Paris - Bought from Michael's craft store - 5lbs for $7.49. Drying time (on package) 30-60 min.
Hydrocal - Bought from Amazon - 10lbs for $29.99. Drying time (on package) 20-30 min lukewarm water/15-20 min hot water.
Dap Patch N' Paint - Bought from Home Depot - 32oz for $8.47. Drying time (on package) 30 min. No shrinkage.
When it comes to making a cast of an object, in this case animal tracks, you want to be aware of a few casting material properties: Shrinkage, Drying Time, Material Flow, and In Field Use. Shrinkage can occur as the casting material dries. Often times you will find a shrinkage percentage listed. Drying times will vary and it's important to keep in mind that these drying times are aimed for indoor projects. Material flow refers to the thickness of the mixture; if it is too thick it might not spread and it could ruin the print. In-Field use refers to how easy it would be to use when you're out in the field. Do you need something special for it or no?
I'm going to try these three types of casting materials outside. Day of casting: Temp - 44F with 64% humidity and light wind, Weather Conditions: overcast with a little sun, and start time: 3:48pm. I bought a bag of sand (50lbs) and mixed it with a little water (40oz), just enough to make it more stable for making a track. I lined boxes with plastic, added the damp sand, and made a shoe print. I used one of my trail running shoes since it has definite tread on the sole.
After removing the set up casting material from the damp sand, I gently brushed off the excess bulk sand from the underside and let them continue to set up inside overnight. This allows the casting material to set up and it also allows the sand to dry out. The next day, in the morning, I brushed the prints again with a paintbrush.
My Results:
Before I share my results, please note that below I have details and final dry casts alongside the shoe I used.
Hydrocal - Hot Water. This set up the fastest (1 hr) in outdoor conditions and provided a quality cast.
Hydrocal - Ambient Temp. This set up the second fastest (1 hr, 15 min) in outdoor conditions and provided a quality cast.
Plaster of Paris. This set up the third fastest (1 hr, 20 min) in outdoor conditions and provided a great cast. This is super easy to find and for the weight, it's cheap. It took 5 more minutes than the hydrocal with ambient temp water, but the availability and price make it almost a tie for 2nd place.
DAP Patch N Paint. This set up the slowest. It was outside for 2 hours, then brought inside for further drying. It is super lightweight, easy to find, and cheap. Perhaps needs more field testing for better or more proficient use.
Plaster of Paris
My initial thoughts regarding plaster of paris is that it's fine in a pinch, but it takes too long to set up especially if you're outside. An upside for plaster of paris is that you can find it at hardware stores and craft stores for cheap.
The mixture I used was the recommended 1:1 ratio. For this, I mixed 16oz of plaster powder with 16oz of water. If I was going out in the field, this wouldn't be hard to carry. The packaging says that it should be set up in 30 minutes, to the point where it can be removed from a mold, and then it should be left for 24 hours to fully set up and become dry/firm.
I started the Plaster of Paris at 3:48pm. I checked it at regular intervals. At 4:55pm it was movable, but could still use a little more drying time. By 5:10pm this is ready to move. OUTDOOR SET TIME: 1hr, 20 min AFTER DRYING WEIGHT: 25.26oz
Issues: None. I'm familiar with this from previous use.
Hydrocal - Ambient Temp
My initial thought with hydrocal is that I've never used it before and I hope it works better than plaster of paris. It's not super pricey for the amount you get, but you do have to order it online. The hydrocal packaging mentions two different setting times depending on water temperature, so this is going to be done twice.
The mixture I used was the recommended 41 water:100 hydrocal, ratio by weight. I pulled out my food scale and measured out 400ml of hydrocal. This means that 40% of that weight equals 160ml, which is what I measured out for the water. This water was at room temperature. Working time is supposed to be 20-30 minutes.
I started the Hydrocal - ambient temp water at 3:55pm. I checked it at regular intervals. At 4:55pm it was movable, but could still use a little more drying time. By 5:10pm this is ready to move. OUTDOOR SET TIME: 1hr, 15 min AFTER DRYING WEIGHT: 17.25oz
Issues: A little clumpy. It felt like I had to stir more than with the plaster.
Hydrocal - Hot Water
My initial thought with hydrocal is that I've never used it before and I hope it works better than plaster of paris. It's not super pricey for the amount you get, but you do have to order it online. The hydrocal packaging mentions two different setting times depending on water temperature, so this is going to be done twice.
The mixture I used was the recommended 41 water:100 hydrocal, ratio by weight. I pulled out my food scale and measured out 400ml of hydrocal. This means that 40% of that weight equals 160ml, which is what I measured out for the water. This water was boiled in my electric hot water kettle. Working time is supposed to be faster than 20-30 minutes, but the label doesn't tell me a time frame.
I started the Hydrocal - hot water at 3:58pm. I checked it at regular intervals. By 40 minutes, it could possibly be moved, but it was still a little wet. At 1 hour it was definitely firm enough to move. OUTDOOR SET TIME: 1 hour AFTER DRYING WEIGHT: 18.17oz (there was a little blob on the side)
Issues: This was a little clumpy. I tried to get the clumps out and move fast with this. Also, I used cheap plastic liners for painting and the water temperature slightly melted the liner.
Dap Patch N' Paint
My initial thoughts on Dap Patch N' Paint is that I wasn't sure if it was going to work. I was worried about it distorting the track. It's the closest thing I could find to Dap Presto Patch, which is mentioned on the Sasquatch Tracker website. Dap products are easy to find in hardware stores and they're fairly cheap.
The mixture I used was straight from the tub and gently pressed into the track. It is super lightweight and there is no mixing. For field work, these are two thumbs up.
I started the DAP at 4:00pm. I checked it at regular intervals. At 4:55pm it was starting to dry, but was still pretty soft. At 6:00pm the DAP was still pretty soft, so I brought it inside. At 7:00pm it seems like it's starting to set up. OUTDOOR SET TIME: 2 hours outside, 12 hours set up inside. AFTER DRYING WEIGHT: 9.52oz
Issues: I just scooped this out with my hand and pressed into the print. It sticks to hands a lot. If I was going to use this, I would have a set of nitrile gloves and a piece of plastic (like a plastic bag or something) to lay over the DAP for easier compression into the track. Takes forever to dry in outdoor conditions.
NOTE: This DAP Patch N' Paint has it's good points and bad points. It's super lightweight, you don't have to mix it with anything, easy to find, and it's cheap. It took forever to set up and it's soft enough that it sunk during drying, distorting the track. It's still super light after drying.
I feel like I need to test this again. Maybe it was just too thick in the track or something. It did manage to pick up quite a bit of the track.