Printing Specifications

Below is a brief guide to help you in preparing your artwork for screenprinting.To get your artwork onto fabric involves taking a digital image and outputting it to film positive for screen-printing.

For the best results one screen is used for each separate colour, although where there is a wide range of colours four-colour process print can be used, subject to a few limitations (see below).

In order to attain accurate colour reproduction it is sometimes necessary to lay down a white base or background prior to printing artwork. This is especially the case when printing a dark colour onto dark fabric.

Artwork should be CMYK or spot colour. The appropriate PMS (Pantone C) numbers should be sent to us for as accurate colour reproduction as possible.Please use the solid coated range.

Copyright and intellectual property of all supplied artwork are the responsibility and guarantee of the customer.

We would prefer your artwork to be in an Illustrator file or an eps laid out as you require it to be printed out i.e. at the orientation you desire and with dimensions at 100%. Please try to send the original artwork as opposed to an export of the original.

The standard lines per inch, lpi, of a screen print design onto fabric is generally 35 to 45 lpi. Lpi is generally about half that of dpi. It is when line art starts reaching a frequency of 60 or greater that images become unacceptably distorted when screen-printed. The distortions are the result of what is known as dot gain, where ink pools or collects creating blobs and blotches.

The lpi for screen printing onto fabrics is very different from that of lithographic art standards; the following two paragraphs are taken from Macworld Photoshop 6 Bible, Deke McClelland, IDG Books Worldwide Inc., 2001

Most experts recommend that you set the Resolution value to somewhere between 150 percent and 200 percent of the screen frequency of the final output device. The screen frequency is the number of halftone dots per linear inch, measured in lpi (short for lines per inch). So ask your commercial printer what screen frequency he uses—generally 120 lpi to 150 lpi—and multiply that times 1.5 or 2.

Want to be more specific?

For high-end photographic print work, it’s hard to go wrong with a Resolution value of 267 ppi. That’s 200 percent of 133 lpi, arguably the most popular screen frequency. When in doubt, most professionals aim for 267 ppi.For screen-printing, generally the simpler the design the better it will translate to the screen printing process, although some process jobs can attain a high level of clarity and detail. Many images that are set up for CMYK offset printing cannot be reproduced to the same quality when screen-printed; in fact many of them look awful. If you bear in mind that the ink forced through a fabric screen is on average 20 – 40 times thicker than the ink used in offset printing, you will appreciate the limitations, but also striking possibilities of screen-printed artwork.

If your artwork uses photographic art there are a number of factors you should consider to ensure accurate screen-printing. These factors include dot gain & loss, CMYK screen values and the output curves of the digital image.

When artwork is at the higher end frequency (or in other words the dots are smaller) as is typical for photographic art and the artwork has originally been made for lithographic output, adjustments really need to be made to the screen angles of the CMYK gamut. Convention dictates the following angles for screen-prints: Y = 7.5°, C = 22.5°, M = 82.5°, and K = 52.5°. These are generally available from the Print Options menu in most image manipulation programs such as Photoshop.

Factors to consider in all lineart are the stroking and trapping of colours that touch each other. One colour is expanded (stroked) out and then overprinted (trapped) by the other colour. This ensures that the lineart is clean and there is no gap showing between the colours.

All fonts should be outlined. This reduces the risk of delay in matching up fonts where not all aspects of a font’s makeup are supplied. If fonts are to be sent, please ensure that screen fonts are included with the suitcase. Note that they must be Macintosh compatible. The basic specs for minimum font size, lineweight, & various coverage areas are 10 pts for text (equivalent in size to Times New Roman at 10 pts), 0.75 pts for lineweight. Try to avoid serif fonts, the fine ends often get lost, sans type fonts screen print better. If your font has more delicate lines than that, be prepared for parts of the letters to disappear.

When knocking out through multiple inks, the problem of fill in is accentuated by the problem of misregistration. Avoid multi-ink knockouts for screen art in general, or if you cannot, use strong sans serif typefaces and large point sizes.Dot gain is the name for what happens when a halftone dot prints larger than was intended.

Dot disappearance is the failure to print of halftone dots under a certain weight.

Tonal jump is the sudden increase in dot gain once a particular dot density is passed.

Problems that might occur during the screen-printing process:
1. dot gain of 15% or more, starting in the midtones
2. solid fill-in of dots over 85%
3. disappearance of dots under 10-15%
4. at least one significant tonal jump at around 30%, and a few other smaller ones scattered about.

To avoid, or mitigate, most of the above bear in mind that you should not use smooth gradients for screen-printing. Artwork consisting of gradients will often result in tonal jump and posterisation.

Do not use an image that contains a lot of subtle highlight information in the 0% - 20% range. Dots will likely disappear and cause a visual hole in the centre of your artwork

To reiterate; it is preferable for your artwork to be solid spot colours, note that you can use hues of spot colours to give a very effective impression of colour.

You may also be pleasantly surprised to learn that it is possible to create an image that looks quite intricately shaded, keep your image dpi at no less than 300 dpi, we'll change the line screen.

We hope that the above has been of assistance. If you have any further questions contact us.