Butt or Trap? Spot colours.
Submitted by Steve on Monday, 27 April 20094 Comments
This is first thing we think about when separating your design for screen printing.
Butt or trap registration? What are they?
- Trap Registration.
This is essentially an overlap. When screen printing on dark garments all colours require a white underbase to improve there opacity. Without the overlap there is a danger the white will still be visible at the edges of the colour printed on top. Screen printing on textiles is a tricky business and very slight movement can occur in the fabrics and the screens, especially when heat is applied (the white underbase needs to be flash dried before applying the colours, some T-shirt brands will shrink at an alarming rate under this type of heat) trap registration creates a margin for movement. If applied correctly the overlap will be barely visible on close inspection. In a programme such as illustrator you can take the underbase back using a stroke of 0.5 . - Butt Registration.
separations set up to register perfectly without overlaps. This type of registration is hard to achieve, but well worth the extra set up time on longer print runs on light shirts, especially when using water based inks. It helps to prevent bleeding of colours and the need to flash cure between colours. This type of separation can also be used when discharge printing. Butt registration requires a perfectly aligned printing press, if you have uneven palettes and worn registration pins you may want to stick with the afformentioned Trap registration.
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Hi, Yes I found your site interesting, Registration is always a Key factor, in all Printing, more so, for 2 plus multi colours and of course waiting for one to dry before you can apply the next, then shrinkage could occur. ?
also overlapping colours is great if you use a colour to blot the other out (as Black), but if you use a lighter colour, you end up from using 2 colours-you get 3 colours as from the overlap.
So to do a but up to a colour? must be hard? especially in, butt up same colour to the left and right of the 1st image colour, On a long run, with Humidity, that affects your stock.
At 58 years old, I used to be (redundant now, due to this Digital age) an Offset litho Print Machine Minder, on a SRA2 Kord, and printing reversed writing out of printing 4 colour half tones in opposing corners of the sheet guides, can and did cause real problems.
So you have “Trap Registration”, would that be an image of your work shone down as a still image, to place the next colour to print?
I am just interested, as your work seems interesting, as I give thoughts back to my old job.
Then I was always in my job, to turn out work only that I would like done for me, in that way I felt I was giving my best.
Hope you have not thought, what a nutter emailing in, it’s just pure interest from me.
All the best,
Lawrence.
Thanks for your comments Lawrence, artwork is key to a good print, I agree, the overlapping of translucent inks is a great technique for achieving more colours with less screens. Although screen and litho printing are worlds apart in some respects there are many principles shared by both that will never change, and although the computer age has transformed both industries quite dramatically, a bit of old school, hands on, know how never goes amiss.
Thanks for this article, It gave me some more insight in the printing process. As a designer for tees I’m trying to get a better understanding of these things so we can deliver the artwork in aprinter friendlier state.
A related question: Is there an optimum stacking order of colours?
For example: would you always print the lightest colour first and end with the darkest colour? Or the other way around? Or does it depend on the artwork?
We sometimes have photoshop designs where thin white linework overlaps bigger solid dark shapes, destined for, say, an orange tee.
I wonder how a printer would prefer to handle that?
Hi Esta
We generally print light to dark, there can be some variations on this. T shirt Printers always use two whites when printing plastisol inks on to darker shirts, a base white which goes under all lighter colours which might be altered by the underlying shirts colour, then a highlight white which is applied later or last in the sequence. In the example you mention the fine white lines could be applied on top of the darker colour, leaving it as a solid block. It is also possible to print the dark colour over a solid white leaving the lines to show through. It very much depends on the inks your printer is using and his machine/carousel set up. These variables have been dealt with in different ways by different printers, this is the reason many screen printers prefer to take care of more complex separations in house.
If you wanted to print using discharge inks, only one white is applied, there would be no layering of ink, so butt registration is required, and a very accurate press…I think an article on colour sequences is required, thanks for your comment, I hope this helps a little.
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