Grinding and Polishing Micromosaics

Polished micromosaic with a landscape scene

Historically Roman Filato micromosaics were often but not always ground down and polished to a mirror finish using coloured wax as grout. This technique of grinding and polishing came from the need to make the mosaic look as similar as possible to a painting. Gaps would have been a problem in these mosaics compared to traditional hand cut mosaics where tesserae and gaps were equally important.

Detail of Alexander the Great in the Battle of Issus mosaic from Pompeii, House of the Faun 1st Century BC

In traditional mosaics, like the one above which is Opus Vermiculatum, the gaps between the tesserae are essential to being able to "read" the mosaic. We can see the directions of the lines referred to as the andamento thanks to the gaps. These gaps help us understand the anatomy of an object in mosaic. It has historically been an integral part of mosaics.

When filato micromosaics were created, they were a response to the issue of the deterioration of paintings in St Peter's Basilica, The Vatican. The filato micromosaics had to closely resemble the original painting without any gaps, leading to the development of the grinding and polishing technique.

The filato technique along with the grinding and polishing process as well as the production of specific colours and materials have all been kept a secret within the Vatican for centuries. Only recently have some of the techniques been shared outside the Vatican walls, however many of the secrets remain. It is difficult to say if the techniques within the Vatican remain or whether they've been lost. What I know for sure is that when I've asked around about the grinding process not many people have answers and what little info they give me is sometimes incorrect or mysterious - with materials that are unheard of for example.

The grinding of filato micromosaics did not stay the norm. I believe it started as a basic step to all filato micromosaics for a time since there are numerous fairly simple micromosaics that were obviously being sold to tourists with scenes from Rome like with the Vatican or Roman Forums which are polished and waxed. However it is clear these were quick to make compared to their earlier counterparts.

Filato micromosaic of roman forums set in goldstone glass

As seen in the filato micromosaic above the tesserae are quite large, especially the mixed tint pieces that make up the architectural elements. These small but fairly roughly made filato micromosaics are polished and you can clearly see the coloured wax between the gaps. It is especially visible in the dark green at the bottom and the light sky blue wax at the top. Fact is, grinding, polishing and waxing take an enormous amount of time. The main one being waiting for the stucco to harden completely. This process cannot be attempted before it has completely set otherwise tesserae come out, the stucco rises to the surface and the micromosaic could become compromised. Not only that but the grinding must be done by hand. Doing it on a grinding wheel could also compromise the surface. Any grit that gets caught could irreparably scratch the surface of the filato micromosaic.

There is a lot of unpolished filato and micromosaic jewelry, famously Castellani jewelry is as far as I can tell mostly unpolished.

Castellani bracelet featuring a moth

As you can see in this image above the light reflects irregularly across the surface because it is not polished. The pieces are set very evenly and tightly and may look polished to the untrained eye but it is not polished.

detail of Castellani Bracelet

Nowadays there are very few artists who continue the tradition of grinding and polishing micromosaics. I can only think of one major name (and perhaps one or two smaller names) who polish pieces to a mirror finish, and that's Maurizio Fioravanti with master goldsmith Virginie Torroni who together created Vamgard. They make small collections of micromosaics set into various precious and semi precious stones which are all polished down together.

Vamgard Spider ring (photo credit @SymbolicChase instagram)

Sicis and Le Sibille are both examples of companies that do not polish their pieces at all. Below you can see clearly the floral design in the heart shaped Le Sibille earrings are not polished. They are masterfully made and level but not polished.

Le Sibille heart shaped floral earrings

In my experience Polishing is time consuming not only for the wait time and the fact that it is done by hand but each tessera needs to be placed perfectly level with the next. If there is a tessera that is lower than the others you need to grind down to reach that one tessera. It is painstaking to get the surface to be perfectly level. There are tricks but the skill required to reach these tricks is still awe inspiring.

What are your thoughts on grinding and polishing? Do you prefer them to look like paintings and barely any tesserae visible or do you like the subtle sparkle of an unpolished piece? Let me know in the comments!

I love them both but there is something that is lost when it is polished. There's that sparkle that I love with slightly different reflections of light on the tiny surfaces. It's a hard choice though!