"What is that thing?"

"What thing?" I ask, not sure what in the field jacket the person is pointing to.

"That!" they say insistently. "The white thing! Is that bone?"

...you would think I would get the question right away at this point. Nope. They get me every time.

I realize that not everyone has been into the field, or even done prep work, so I suppose that's a fair question.

Seeing as I haven't done this here at Ashfall yet, these pictures are from my Wyoming trip two summers ago with Casper College, led by Dr. J.P. Cavigelli. It was the first time that I did this, and so there are pictures (actually, my first time doing this was on a much smaller jacket, but there isn't as much photo evidence of it, and its just not as impressive as doing one this size.)

This is a field jacket. The dark brown in this case is bone, the grey-ish stuff is rock (or, as we call it, matrix), and the white thing is the field jacket. A field jacket is made out of plaster and generally either burlap or some other sort of fabric-y material. The first one made like this was actually an accident, involving trying to get plaster to stick to a specimen using burlap, and then not being able to get the burlap off. Gotta love trial and error.

So what else do you know of that would require plaster?

If you said a cast and are thinking of the last time you broke a bone, then we are on the same page! (If not, turn the page. There ya go, see it now?)  The whole purpose of a cast is to hold everything in place until the bone has healed. Well, we don't want fossils breaking in the first place, because if they do, they aren't going to heal. But rock does a pretty good job of holding bones together, as long as you keep the rock as it was in the field. And so you need a very tight field jacket.

First, you expose the fossil. You don't dig under it, but you dig around it (this is called pedastooling.) Then you cover the fossil in a separator (generally either tin foil or toilet paper.) Easy enough. A lot of people ask about the paper or the foil they see. Well, there you go.

Then comes the messy fun part. This is the part that involves water, plaster dust, mixing it with your hands, dunking fabric in the plaster, squeezing it out, and covering the fossil with it. You can't be afraid to get it on your hands, and it had a bad habit of getting on my hat while I was in Wyoming, too. All jewelry, if you dared to wear any in the field, needs to be removed for this. Any stones will stick to the plaster, and the plaster will ruin them. Not pretty. And all of this has to be done before the plaster sets. Once it sets, its useless. Fun fact: plaster takes so long to set in Antartica, if it sets at all, that paleontologists there don't use it. In fact, most of them use duct tape! ...it makes for a pretty lousy field jacket, actually. But it's better than nothing... maybe...


This part is almost as important. Messing with your fellow paleontologists. In Wyoming, this involved an obligatory hand shake. In Utah, well... it meant occasionally splashing it on those around you or giving them a generous pat on the back (we also did this with mud on rainy days in Utah...)

It's not totally evil. Actually, as the water evaporates, it cools you off, about like sweat would. On a hot day, its a good way to get that feeling without wasting water (a big, big no-no in the field.)

So the jacket dries and stabilizes, and then you flip it over. Depending on how far it has to travel, you may or may not add plaster to this side. But when you get into the lab, the underside is the side that is excavated from. Jackets this size can easily weigh over 50 pounds. ...or 100. I forget with this one, actually. But a large enough jacket requires a lot of man power and sometimes (if you are lucky) a machine to move it. Then you stick it in the car and don't move it any more than you have to until you get back to the lab. Ah the lab. A nice, controlled environment where if anything goes wrong you can douse it in glue in the comfort of air conditioning. Translation: its a controlled environment. By the way, like a doctor would with a cast, we use a pretty serious looking saw to open these sometimes when we do put plaster on both sides. In fact, its the same saw. It looks scary. Kids hate it. But its really just a blade that vibrates back and forth, designed to cut through anything that resists it (something hard) and nothing that doesn't (something soft.) Basically, if the doctor messes up and hits skin, it won't hurt you!