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Creating mineral bases using Fimo Clay

Last Updated: 26th Apr 2011

By Jolyon & Katya Ralph

Creating mineral bases using Fimo Clay

Some minerals are difficult to display without a custom base. There are many people providing custom bases, but for those on a limited budget (or who enjoy being creative), you can make your own using Fimo modelling clay).

Fimo clay is simple to work with, inexpensive and can be fired in a domestic oven for 30 minutes at a relatively low temperature. Crucially it does not shrink when heated, so you can create a base, fire it, and it will be a perfect fit for your specimen.

So.. Here is my first attempt at making a base. It took me a total time of about 45 minutes.

1. Break off a piece of the clay. I'm using a glazed bathroom tile to work the clay on - this is ideal because it can go straight into the oven on this tile.

Break off some clay

2. Knead the clay to soften it.

Kneading the clay is essential.

3. Roll out the clay. Keep kneeding and rolling the clay until it is elastic.

Rolling the clay.

4. Push the clay into a lump

Creating a mineral base using Fimo clay

5. Push your specimen into the lump of clay. Adjust the clay so it can properly hold the specimen, but you must be able to remove and insert the specimen again!

This specimen is a native copper from Dzhezkazgan, Kazakhstan

6. Bake the base on the tile (without your specimen!) for 30 minutes at 110 degrees Celsius (230 degrees F). When it comes out, leave it to cool for 20 minutes.

It looks the same after baking, as it should!

7. Test your specimen in the base - it should fit perfectly!

Yes, it fits

8. If you want a neater base, you can trim down the baked clay, it's not hard to work with. You'll need to judge how much you should leave to securely keep the specimen stable. I just used a normal kitchen knife to cut through the clay. it has a consistency more like a hard plastic than baked clay.

But it's still a bit ugly...

9. You can sand down the sides if you want it to be nicer. I could trim down the top and sand that down too, but I am uncertain how much stability would remain if I did this.

Sanding down the sides.

10. The finished base.


11. Testing the specimen again. It doesn't fall over, I haven't trimmed too much!


12. And into the cabinet it goes.

Now. this is my first attempt, and with more experience and more patience I think it would be possible to use less clay and make less obtrusive bases than this - but it works fine and keeps the specimen safe.

In the cabinet

Hope you enjoyed this!

Fimo clay is available in many places, but in the UK you can buy it mail-order from EJR Beads - which is run by my sister (who is somewhat of an expert on Polymer Clay having written two books about it!) You'll want the 'Fimo Classic' blocks, which are available here: - I used the "00 Translucent" for this experiment - as you can see it's not VERY translucent, I have also got a block of white clay to try, but you can choose the colours that you feel are appropriate for your specimens.


Article has been viewed at least 14314 times.


Interesting! Thanks :)F

Frank de Wit
26th Apr 2011 3:04pm
another brand of similar clay is Sculpey brand. depending where you buy it and how much you think you will use there are larger packages available.

Matt Neuzil
26th Apr 2011 5:43pm
Yes. My sister (who is the expert in all these things) claims Fimo is beter than Sculpey, but I suspect there's not much to choose between them when making mineral bases. You can easily make four or five bases out of a single block which costs about $2.50.


Jolyon & Katya Ralph
26th Apr 2011 7:07pm
Thanks, Jolyon. Very useful article!

Alfredo Petrov
26th Apr 2011 7:29pm
Thanks for the info Jolyon. I recall seeing something similar from an old issue of MinRec, but it was a bit more complicated than your technique. This looks like it could work out quite nicely. Up until now I have been using clear acrylic squares with mineral tack or earthquake gel, but I like the idea of the custom fit on these. I have to look into where I could find something like this here in the US. Craft store perhaps?

Scott Sadlocha
27th Apr 2011 2:56am
Yes, craft or art supply stores are the place to find it. A small bead of mineral tack can help hold the mineral in place. If you need a bit more stability, you can mount this base on another base with double sided cellophane tape.

David Von Bargen
28th Apr 2011 1:54pm
Just a note to let people know that currently Michael's (an arts and craft store chain in the USA) has a 50 percent off sale on 2 oz blocks of plastic polymer clay for all of the makers they stock. This includes Fimo, Sculpy and what appears to be the store brand Craft Smart. I bought 4 blocks each of the black and white colors of the Craft Smart brand as they were at least 50 percent cheaper than the other brands.

I figure that I would choose a color for the best contrast, hence the black and white colors. I figure for example a bright orange mineral would best be displayed on a black base especially if it has no matrix. Clear minerals are a bit tricker as I guess I will just have to see what looks best for a very nice terminated bicolor Tarryall topaz crystal that I found at Joe Dorris' Topaz Mountain claim during a club trip.

James Pool
25th Jul 2011 7:23pm
Great idea! I like how the specimen can easily be removed, without leaving sticky bits of tack stuck to it and risking damage to more fragile specimens as happened to me once before with a brand new specimen, I went to lift it of the tack so i could examine it and it just came apart, also i hate the smell of blue tack, I dont know where to get mineral tack from and i dont know if that has a smell either.

Jason Evans
3rd May 2012 8:58am
Interesting, Especially that I do not know professionnal base making at the doorstep.
For larger speciments requiring an heavier and larger base, is the cooking as easy, without cracks?
Since that stuff is not so cheap, does anybody know in which kind of store to find this in large quantity and black color in Belgium (or France, Netherlands or Luxemburg), I guess it would be cheaper than a mail order.
Many thanks
Valère, Belgium

Valere Berlage
21st Aug 2012 4:17pm

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