A tale of printing, sardines, and tuna

I was aware there are canning archives in Vila Real de Santo António but hadn’t quite realised there was a tiny museum too. In this tiny but fascinating museum they take you through the complete canning process, starting with the tuna fishing and finishing with the sealing of the tins. All of it interested us, but the section on tin design, printing (lithography) and packaging really caught my eye.

I am going to attempt to explain in detail how they produced the designs for the packaging, but before I do please note that whilst the museum is fascinating their explanations are not always the easiest to understand. Nor do they answer all of the questions so be prepared to be as confused as I was at times!

Lithography was invented in the late 18th century in Bavaria, and offset lithography remains a printing technology to this day. When it was invented though the printing plates were made of limestone, and in fact lithography means ‘printed from stone’. Something I only realised on our visit when I saw stone after stone in the museum! We thought it quite extraordinary how many have survived.

Lithography printing is a type of ‘reverse imaging’. The first step is for the ‘image’ to be drawn with oil or wax onto the surface of a completely smooth and level limestone. The stone is then treated with a mixture of acid and gum arabic. This treatment causes the portions of the stone that are not protected by the grease-based image to be ‘etched’.

The stone is then moistened with water, and the areas ‘etched’ retain the water so when the oil-based ink is applied it only sticks to the areas not ‘etched’. Paper is then placed on top and the ink is transferred producing a printed page. Hope that explains the process, but if not and you have a moment take a look at this video from Minneapolis Institute of Art;

The print the artist creates in the video is lovely, but when compared to the ones that the sardine and tuna canning industry once created for their tins you realise it is incredibly simple. It is also a single colour. Multiple colours are more complex and expensive as a lithographic print with multiple colours requires multiple stones. However this wasn’t how the canning industry produced multiple coloured cans.

In canning the lithograph was used to reproduce the drawing in black and white as many times as needed to fill the the metal plate from which the cans would be made. So if 22 lids could be made from one tin plate, then the drawing would be reproduced 22 times on paper from the lithograph.

These 22 paper prints were then chemically transferred to a zinc sheet, and then that zinc sheet was used to transfer the now one ‘drawing’ of 22 tin lids (or bottoms or sides) to multiple tin plates. If only one colour then the multiple tin plates could go directly to the tin manufacturing department to be made up into tins. If the can design was multi coloured then the transfer from zinc sheet to tin plate was repeated as many times as the number of colours in the drawing.

Hope I have managed to make sense of it all for you! Just to add to the confusion some of you may have spotted that the majority of stones, including the one on the lithograph itself, are much bigger than the cans we buy. That’s because most of the stones I photographed would have been used for advertising and commercial cans (we think!). There were a few stones with smaller can sized etchings, and we also spotted a printed sheet, however we couldn’t see many examples so either they were hidden in the stone stores or they haven’t survived in the same numbers.

And finally if you are still with me, and are wondering why the museum is here, well Vila Real de Santo António is the birthplace of fish canning in Portugal. The first factory was opened here in 1853 by Ramirez . They are considered to be the original Portuguese brand of canned fish, and they also claim to be the world’s oldest producer of canned fish. They were not the only company though; there were once hundreds canneries in the Algarve, most of whom were Italian, French or Spanish, all producing canned fish and exporting around the world.