I’m making some ceramic mosaics and wish I could do it authentically.
When the Greeks and Romans made mosaic faces, they came out in very subtle shading and all pieces fit tightly in arcs and patterns that convey shapes.
Like this portrait of Medusa
Did they make a bunch of colors and then cut them to fit, or did they work out the designs all in plain unglazed tiles, and then color the tiles and fire them as a group?
Tesserae [the little tiles] were a common product, and came in a range of colors. Since the workers making the mosaics knew they were doing faces [or clothing, or bunches of grapes] you just get a selection in the right colors, and tap them into the shapes you need.
the most spectacular mosaic I ever saw was a small piece, about a meter square is remaining, that the tesserae were semiprecious stones. Not sure if it is still on display at the Louvre or not…but incredible.
A few of the mosaic ceilings in Istambul’s romanesque churches were clear colored glass backed with gold leaf. Very nice.
The second method was also done.
Since aruvqan mentioned churches, I’ll compare that second method to stained glass. Originally, stained glass was done piece by piece in geometric designs. When faces and costumes were added in detail, then a face, a hand, etc. would be painted on a single pane after the pieces were cut.
In the same vein, some ancient mosaics have pieces where a star or an eye, for example will be painted on one tile, and a crown on just a few, but having shadings on each piece. This was required for smaller mosaics or the details would become too hard to create with normal size tiles.
There was a gorgeous tiny mosaic of a face from Pompeii that I have tried to find on the Internet. It was used as the symbol for the traveling exhibit “Pompeii 1979” that went around the US about 25 years ago. The mosaic was only a couple of inches (at most) on a side, but was made of a great many tiny shards with tiny color gradations. It looked much more like a painting than the example in the OP.
I got the impression that the mosaic was actually made from naturally-occurring stone, not fired ceramic, though I may be wrong. If that’s the case, then clearly the coloring was the result of painastakingly finding the right colored stones and cutting them.
I’m an amateur mosaic artist myself, I’ve done a few pieces for personal pleasure, so I might be able to help you.
You appear to be asking two questions at once, they’ve sort of run into each other.
First, you wonder how they got the proper mix of colours for a picture. What I do - and I’m guessing that the Romans did the same - is to keep a range of colours in stock, and pick out the ones I need for a particular picture.
Also, you wonder about how they got the tiles to fit. There are three ways of making a mosaic picture.
** The direct method ** Here you start with a smooth flat surface, such as plaster or wood. You draw your design directly onto the surface. You cut your tiles to fit the picture. You glue the tiles to your picture. Then you grout to fill the gaps between tiles.
The indirect method This is good when you have a large design covering a floor or wall. It can be assembled in sections in the studio and moved to the destination. Here you draw the design onto some backing material. Stick the tiles onto the design. Then you can move your design wherever you want it, and stick the whole thing to a floor or a wall. Again, grout between the gaps.
The Reverse Method
ahem, as I was saying …
**The reverse method ** Here you draw your design onto paper, stick the tiles onto your design. Then you make a bed of wet tile cement, turn your design upside down and push it into the cement. When the cement dries, soak the paper until it peels off. This is the method that I use.