Copyright 2001, Gripper Products
For those of you interested in how Grippy and Cormo come up with the stuff in their science
theater projects -- here follows their research so far on pykrete.
To make pykrete I needed to get sawdust. Called 3 lumber yards. The 3rd said to call back the
next day. Then they said to call about 4 pm and they'd let me know. At 4 pm they said they had
one bagful. I went with one bag. I could have brought 5. But now I'm making pykrete.
Eccentrics said the pykrete was 14% sawdust. It didn't say by weight or by volume. I'm making
pykrete in milk and orange juice cartons. They hold 64 ounces, so 9 ounces of sawdust is about
14% by weight. I weighed the carton -- 2 ounces -- and set the balance to 11 ounces. I had to
keep mashing down the sawdust to get the balance up to 11 ounces. Then I added water. There
was room for 7 cups in addition to the sawdust. I also made a control of plain ice water.
This size block of ice does not freeze quickly. I started one set on Wednesday Sept 25. On
Friday, there were still bubbles in the control ice that moved when I shifted the carton. The
carton of pykrete has split on one corner. It must expand differently from the regular ice, which
is growing taller as it freezes.
weight with carton (2 oz):
with sawdust 3 lbs 14 oz.
without sawdust 3 lbs 11 oz.
at 2:08 PM water is 19°C and control ice is completely melted. Ice lasted 48 minutes Pykrete is
shedding sawdust, but is intact -- approximately ¾ original size. It is soft to touch and bits of
sawdust brush off if I rub my hand on it. .
5:38 PM, pykrete completely melted. Water temp 21°C. About 4:30 PM, I found the pykrete
sunk to the bottom of the tub (approx 8 gallons of water). I reached in and shook it -- lots of
soggy sawdust fell to the bottom of the tub. Then the pykrete floated again. Pykrete lasted 3 hrs
and 18 minutes.
Pykrete update. 10/05/96
Next, repeated the above with the pykrete. The pykrete barely dented with the weights dropped
crossways on it from 2 feet. Again, dropping the 10 and 15 and 20 lb weights from 3 feet
end-on barely dented it. Then Steve, a visitor, dropped the 20 lb weight end-on from 5.5 feet and
the ice sheared -- a flat horizontal break, about 1" below the top surface. The top sheet broke
into two pieces at the point of impact.
Freeze ice and pykrete in freezer compartment of refrigerator in ½ gallon milk cartons. Place
milk carton of frozen pykrete in a plastic bag to catch leaks. Measure room temperature with
thermometer. Place bag and box and thermometer in cooler.
temp in cooler:
2 PM 22°C
4 PM 11°C
7 PM 12°C
10:45 PM 11°C
12:36 PM 12°C
5 PM 11°C (note I can poke a toothpick all the way into the sawdust. There is about 1" water in the bag around the box)
9 PM 13°C (more water in bag)
2:24 PM 18°C (this is room temp today)
duration of experiment: 2 days
6:35 PM 10°C
9 PM 11°C
8:45 AM 11°C
10:05 AM 12°C
2 PM 13°C
8 PM 14°C
8 AM 15°C
2:20 PM 18°C
duration of experiment: 2 days
The arctic picnic bag is so well insulated that it negated any difference in the properties of ice
8 PM Placed a 1 cup baggie of Rubbermaid brand blue ice in freezer. Made up a baggie with 1 cup tap water and another with 1 cup sawdust plus enough water to saturate the sawdust (approx 7 ounces.)
Placed them in freezer.
8:30 AM Removed all 3 baggies and placed them on table top. Room temperature 18°C.
Freezer is -16°C. Note blue ice feels more dense than ice or pykrete.
Again using the Arctic Picnic Cooler
1 quart pykrete in 1 quart freezer baggie inserted 2:11 PM temp (18°C.)
Both blue ice and pykrete keep the cooler below room temperature for approximately 24 hours.
Placed 1 cup pykrete in a baggie and 1 cup Rubbermaid Blue Ice in a one-cup bag (as sold) on a sheet of plastic on my dining table, and stuck a thermometer under each of them. Recorded time / temp points follow:
Conclusion: The blue ice remained usefully cold from 9:04 AM until approximately noon -- about 3 hours. The pykrete remained usefully cold from 9:04 AM until approximately 3:00 PM -- approximately 6 hours, or twice as long.
Note: Folded newspaper in a ziplock freezer bag, wet with just enough water to saturate the newspaper, and then frozen, is also effective.
Additional information about Pykrete: