This is an area which I’ve not placed as much emphasis on as I should have done. In making copies of Roman mosaics after knowledge of The Rules this is the most important area. If you want to know how good a copy of a Roman mosaic is, look at the background. If the proper attention has been paid to this then the work is complete.
Firstly we need to look at the original mosaics. As we can see from the images below the background is made up of off- white tesserae and they’re not all the same size. The working size for tesserae (tiles) is 8 – 12mm and with all the tesserae being hand cut using a hammer and hardie each piece is very slightly different in size and shape though all those used will fall into the average size.
Here lies the skill, you need to be able set the tesserae allowing for the slight difference in size but keeping all the time to one, single line. If at some point the size of tesserae used are too large or too small then this has an effect not only on that row but also the next row you set.
If you have a row with larger pieces on the left half of the line and you then start to use progressively smaller tesserae ( and I’m talking 2 -3 mm smaller) which is a common mistake, then the next row below it will get halfway across and will reach an area where you’ll need to set much larger tesserae to avoid the lines beginning to slope upwards.
Or you want to work a little faster so you use tesserae which are just a little too large. This means that the line below either has to have tesserae a lot smaller to stop the line sloping downwards or you allow the line you’re working on to continue to get smaller until it disappears against the larger tesserae above, the last tesserae of this line will be a triangle. The next line below that will be straight but you’ve created a ‘point of focus’ (by the use of the triangle) where one line disappears.
This triangle will creates the point of focus. This one point where the triangle is used will, at some point catch the viewer’s eye. Then, every time they enter the room this point will be the first thing they see.
Another common mistake I see made is when the tesserae are set using pieces that get progressively smaller but longer, i.e. shaped like a brick. A brick wall has a very ‘flat’ look to it and with a Roman mosaic you need to get the impression of depth.
There are a number of other considerations for the background which I will cover in a later article.
The background should be exactly that, background. You shouldn’t notice it but you need to pay attention to it to ensure that you do not create any points of focus. Keep the tesserae within your working size, ensure the gaps remain constant and wherever possible make sure your lines run straight.