Cameo Times is deeply grateful to Julie at the Fontaines Pétrifiantes of Saint-Nectaire, France, for the following detailed information on the technique employed for creating cameos and other items using the calcium carbonate rich water of the local hot springs:

When it's raining the water is going deep down into the ground (in Saint-Nectaire, the water goes approximately 3,000 meters deep). But because of the heat and the carbon dioxide, the water is expelled to the surface as a spring.  Our water is hot naturally (35°C) and very rich in calcium carbonate (we have 2g/liter of limestone). The limestone is perfectly dissolved in the water.  But scientists know how to extract the limestone from the water: by creating a water ventilation [system].

After years of research, in 1821 Jean Serre (Eric Papon’s ancestor) created the first fontaine pétrifiante at Saint-Nectaire: a ladder where the spring [water] rich in limestone could go through and run such as a waterfall!  His research helped him to understand that more the ladder is high, more the piece of limestone left by the water is small at the bottom of the ladder! And the deposit is rare. The more you are at the top of the ladder, the more the pieces of limestone are bigger and numerous!

Nowadays, Eric Papon, (maître artisan en pétrification and owner of the factory) still uses his ancestor’s technique to create two types of objects:

The first one is crystallization: he puts a pottery at the top of the ladder, he turns it every morning so that the limestone layer is the same all around the object during 3 months. When the thickness is enough, he puts the petrified object out of the water, and when it's dry, it is sold in our shop.

The second one is encrusted mould or also called limestone cast: He uses a matrix in copper which was created by an artist, thanks to the gutta-percha he creates a mould.  Making the mould is complicated and needs time and experience.  We have 3 ladders with different heights (14 meters - 25 meters - 28 meters) The more the ladder is high, the more the limestone carbonate [particles] will be small.  Our craftsmen know exactly where to put the mould to get the greatest piece of limestone.  First he puts the moulds at the bottom of the ladder to get the little pieces of limestone which will create all the details such as the face of your cameo.  But if he leaves the moulds always at the bottom, he would need years to get enough thickness.  So after 1mm of limestone is inside the mould (which needs 3 months) he ascend the mould step by step to get bigger piece of limestone and a stronger limestone cast!  That is why the back of your cameo has a depression and is rough!

As with the pottery, he needs to turn the moulds to be sure that air bubbles or gas bubbles won't be stuck inside the limestone which would create a hole inside the limestone cast. 

For the color, our springs are very rich of iron.  To get a white limestone, before the ladder, the spring [water] goes inside a wood shaving gallery to filter naturally the iron!

To get a cameo, we need 12 months of work! And your cameo comes from our place as we recognized the frame.

To know if cameos are in limestone, just look at the back! If it looks like yours [the first cameo shown in the main article], it's limestone!