On this page, we're going to look at how dry transfers are put together:
Letraset transfers (& other transfers, generally) consist of several layers of material:
What does the protective tissue look like in real life? Here you go:
Traditionally, Letraset protective tissues had a distinctive blue colour; in later years, they were more often a neutral grey. Here is a small, recent, transfer both with & then without its protective tissue:
Lastly, the carrier sheet is turned back-to-front so you can see a couple of features of the transfer itself.
Firstly, notice that there is a white background layer of ink behind the artwork (apart from at the edges, which are borders of black ink). This is to give the colours an even background, & to help combat transparency. You don't want the recipient surface to be visible behind the transfer once you've applied it; transfers should normally be opaque!
Of course, this white background is not necessary with monochrome transfers. Because process colour transfers do require white ink, the inks are sometimes referred to as CMYKW (Cyan — Magenta — Yellow — blacK — White).
Secondly, if you look REALLY closely, you may just be able to glimpse the halo outside the black borders of the individual transfers. It's more obvious in some places than in others, but since the halo is intended to be completely transparent, it is necessarily hard to show. You might be able to make out that the area around the black borders is plainer & less textured than the general surrounding area.
To take pity on your eyes, here's a clearer example where the halo is easy to spot:
Patent documents are inevitably somewhat dry, & I'm sure you don't want to read the whole application. Here are some extracts, along with the solitary diagram. The interesting points are that the patent is very limited to start with in its intended scope, & that at the point the application was made, Letraset clearly hadn't worked out all the details of the final product.
Oh, & also noteworthy is that the patent application talks quite a lot about musical notation; that didn't really turn out to be one of the big applications for the technology (but see the bottom of this page)…
The original text of the patent application appears below in italics, with my notes interpolated.
"The receptor sheet 10 is placed in contact with the carrier sheet 13 in the required position, using the guide lines 14 imprinted thereon, with the tacky coating 11 contacting the design indicia 12 printed on the carrier sheet 13. One of the design indicia 12 is then transferred by pressure using the finger-nail or any hard instrument commonly used for burnishing. The receptor sheet 10 is then pulled out of contact, and by its adhesive nature will cause the indicia 12 to be removed from the carrier sheet and retained on the coating 11. By movement of the receptor sheet and repetition of the process the required wordings may be composed. The indicia are arranged on the carrier sheet in one order, e.g. alphabetical order, but are reassembled on the receptor sheet in any required different order."
"For completion, the receptor sheet may have the wax coating 11 neutralised by the application of a wax polish… Alternatively the receptor sheet, which may be a plastic film, may be placed on a base material and laminated thereto by means of pressure or burnishing."
"As noted above, instead of the waxy adhesive being applied to the receptor sheet it may be applied to the carrier sheet. The indicia may then be covered by a non-bonding cover film until required for use. The method of transfer is essentially the same."
"The thickness of the parts, especially of the waxes, is shown much exaggerated in the drawing.
"WHAT WE CLAIM IS: —
"1. A dry transfer material which comprises a coated carrier sheet having printed thereon a plurality of design indicia formed of a film-forming ink, the coating on the carrier sheet and the material of the design indicia being such that the the design indicia may be transferred bodily to a receptor sheet, and made adherent thereto by a layer of waxy adhesive located on the surface of the printed carrier sheet or on the surface of the receptor sheet, on application of substantial pressure to the design indicia, the waxy adhesive being made to adhere only by the application of such pressure and providing adhesive forces greater than the forces holding the design indicia to the coating on the carrier sheet."
To sum up: what makes Letraset transfers work is the following recipe —
That's the main event. Here are the other ingredients:
Picture Credit: The SPLAT Scan Archives — Anatomy Diagram by Tom Vinelott at Triplica.com.
© Tom Vinelott 2021