TINPLATE PRINTING

Tinplate printing is uniquely different to any other type of printing. The metal substrate calls for very different preparation of artwork and a few considerations need to be taken into account.
Whether you use silkscreening or litho printing, there is no ink absorption as you find on a porous medium such as paper. Thus it is advisable not to use very small condensed, serifed fonts when designing something which will have to reverse out of the background, especially if the background is made up of process colours. Your typesetting will probably fill in and be illegible.

When preparing reproduction of can designs you need to swell type with clips or cut back when you have a printed white, all this to make it easier for the printer to get the registration accurate. You can imagine when printing at high speed that the slightest movement can cause your design to have various colours out of register.

Also before printing starts, tinplate is often pre-coated with a transparent SIZE for the 'metallic look' cans or with a thick white COAT of ink to make it easier for the inks to look clean and bright. But even this white COAT is never as white as a piece of paper. But tinplate has a unique feature in that you can use the 'metallic look' as part of your design. Translucent spot colours work very well especially when combined with a printed white on some elements of the design. The printed white which is used behind photographs/barcodes/type etc. on a metallic can, must have a double pass of printed white, so it is usually a more expensive can. Furthermore the double pass of 'printed white' is never as white as a white coat.

You can print any number of colours on your can but obviously the more you have the more expensive the can, as cans are usually priced by the number of print passes required. The proofer will more often than not, do a double pass of a big expanse of colour - the first pass will be a lighter 'dummy pass' and the second 'key pass' will hide any flaws in the tinplate. Spot colours are preferred on a big expanse of colour so that there is no colour variation from run to run. If you have a background CMYK photograph making up the entire design of your can, the first run of cans will all be identical on subsequent runs, if the printer runs the cyan slightly darker or the black lighter, then, when a later-run-can stands on the shelf next to an earlier-run-can there could be colour variations. In order to overcome this problem, Colour Standards are made and signed off by the customer after the first run and kept at the factory for reference. This helps with subsequent runs.