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Friday, 2 March 2012

Simulating a fossil, part 1.

Just jumping ahead a bit, this is what the finished product will look like, after
you have followed the instructions. I had to come back and add this later,
 because when I wrote this part, these things were still being made.

I am going to take this in slow stages, in part because I am actually doing this (again), some 20 years after first I developed this method for a holiday activity at the Australian Museum. My aim was to let visitors experience the slow painstaking grind involved in preparing a fossil. The children who tried it quickly lost interest.

Nothing is ever wasted, and this became part of my rather sprawling and now slightly creaky Science Fun web site.

If you want to go straight to it, remembering that it is less detailed, the link to Let's Fake a Fossil is here.

To be fair, the products of that "faking" process aren't a real fake, and that's why I prefer to call the method a simulation.

The first two pictures, the shots above, though, show things that are most definitely fakes, though they start with real fossils. The problem is that the fossils are glued to a thick stone slab. Look for the thick layer of epoxy glue that attaches them to the slab (if they don't fall off).

The shots above were taken in Morocco, where fossil faking is a fine art, and where you have to keep your eyes out all the time.  Trilobites are the most common fakes, and you will almost certainly end up with a resin cast unless you keep your wits about you. I recommend buying a cheap ammonite (easy to get, and not worth trying to fake).  Then spend some time, tapping it with a finger nail until you know the feel and sound.

Stone goes 'ching!"  Resin makes a dull thud, by comparison. so when you try tapping on a moulded resin "fossil", the feel and sound is quite different.

This blog entry, though, is background about real fossils, like the ones on the right.  Before I explain these, though, an anecdote: I used to work in a museum that was not the sort that had fossils. It had technology, fine arts and other fun stuff, but no fossils or animal bits.

Most museums specialise, but when a member of the public came in with some fossils, seeking an identification, they called me down to the desk as the only likely helper.

I looked at them and commented that he should try the Australian Museum which was the fossil place, adding that the only time I had seen anything like them was on a rock platform near Robin Hood's Bay in Yorkshire, two years earlier.

"Aha!" said the punter brightly.  "That's where I got these!"  The twit had come to the wrong museum, but got lucky, just by chance.

I had identified mine by comparison with public specimens in Cambridge, so I took his phone number, went home, got out the appropriate notebook, and was able to phone him and give him some of the details.  I can't do that for you now, because the notebook is buried in a mass of others, but the fossils in the fourth picture, the one with the ten-cent coin for scale are the real thing.

So are the fossils in the rest of this entry.  I told the story of the last three pictures is a radio talk some years ago, and rather than repeat it here, I refer you to my Devonian Billabong script. You will know when you get to it, because it has larger versions of these three pictures.

Alex Ritchie painting latex over a slab to make a mould.
We went along as a volunteer family to help clean these up, and that's where I learned one of the the tricks that I will be describing here, cleaning out the matrix that can surround a fossil. In the first picture, the brick wall behind the slab gives you a scale.

The second picture has a 20-cent coin as scale (it is about 28 mm diameter, the 10-cent coin above is about 23 mm diameter).

Lighting is important with things like this: always try for oblique light. I learned that as well.

The last picture shows a key element in professional work with fossils. Alex Ritchie is in the foreground, covering a slab with latex to make a mould, so he can produce casts, multiple copies that can be shared. These are not fakes: they can be shared with other museums, and most of what scientists need to see can be learned from the casts.

And as you will see, the idea of casting came to me, a couple of years later.

Next, I will give you a quick run-down on how fossils are formed, because there is more than one kind of fossil, and I provide you with a shopping list.

Click here for Part 2.  Click here for Part 3.  And here for Part 4.  Though it would make more sense to work through in order, getting all the steps!

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