HELP Screen Print Gradients, and halftones

Explorer ,
Nov 20, 2021 Nov 20, 2021

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So, I've had a few jobs in screen printing, one I got fired from because I didn't know what I was doing.  I am now working for another screen printer, and I have a few questions. I was even willing to pay someone to help me for a few hours, but she flaked, anyway. 

 

My problem is, I know the concept of screen printing, i just don't understand how to print the film.  We do have RIP software (wasatch) and I am hoping someone can enlighten me with these questions, i know that if i don't figure this out I will get fired again, and I am scared I don't want to loose my job. 

 

Here are the questions.

1) will RIP software print gradients? I've heard on numerous You Tube videos you have to change the gradient to a halftone, so if that's the case is the film that's got the gradient on it, for example a yellow color, will the film print a yellow gradient/ or a yellow halftone if this makes any sense? 

 

2) I made a design (stupid me) that I don't even know how to print and it makes me nervous, I am going to submit that here.  PLease tell me how this will print. Theres a bunch of offset paths, and when i click on it there are millions of lines, and it scares me! LOL. What do I do to make this a better file to use for print? 

When I look at it to print on the screen in the print box, it's all there and it looks good, but my question is 

are those black dots going to print, I didn't even assign a black color to this piece? ugh. like i'm really confused.  I was thinking what's going to print are tiny holes, instead of dots.  The bottom of basketball is a white outline and the shirt is going to print throug, with the gradient on top and with the letters in gradient as well. 

 

Any help is appreciated. 

 

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Mentor ,
Nov 20, 2021 Nov 20, 2021

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Let me try to help...

 

"1) will RIP software print gradients? I've heard on numerous You Tube videos you have to change the gradient to a halftone, so if that's the case is the film that's got the gradient on it, for example a yellow color, will the film print a yellow gradient/ or a yellow halftone if this makes any sense?"

 

- Screen printing is really quite complex.  So, yes, the RIP will "generate" a gradient, however, you need a RIP that will print separations as "halftones" and send that to you as film positives ( which are then used to make the actual individual screens for printing on garments}.  There is another way, too.  You could export the artwork as a .tiff file and open it in Photoshop.  More on this in answer number 2;

 

"2) I made a design (stupid me) that I don't even know how to print and it makes me nervous, I am going to submit that here. PLease tell me how this will print. Theres a bunch of offset paths, and when i click on it there are millions of lines, and it scares me! LOL. What do I do to make this a better file to use for print?"

 

- You could export the artwork as a .tiff file and open it in Photoshop.  It gets a little tricky because you should size the artwork before Export out of Illustrator.  Open the .tiff in Photoshop ( if you have it and you should ) > Go to Channels > Split Channels ( you should get 4 CMYK channels: 1. file.cyan; 2. file.magenta; 3. file.yellow; and 4. file.black ) > these should be Grayscale files. In your design, if it prints on dark, you will need a flash White underprint channel, to get this, you will duplicate one of the Channels and Invert it.  Consult with a local source to help you with this because it is pretty complex manipulations and there will be some additional retouching, I'm sure.

 

Getting back to your artwork.  In Photoshop, open the Cyan channel > you should see a grayscale version of the separated cyan colors > go to Image -Mode = Bitmap > Resolution = Input - whatever your original file is, Output - 2540ppi; Method = Halftone > Halftone = Frequency - 35lpi ( for mesh of silk screen ), Angle - 75 degrees ( or whatever is suitable for the mesh of the screen and the channel itself ), Shape - Ellipse.  In these steps, you are bypassing the RIP and doing the halftones yourself, but they still need to be output onto clear film for generationg the silk screen(s).  Since you have chosen a field which you have little to no training, no education that we know of, perhaps you may want to get that before venturing into screen print design and prepress. 

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Explorer ,
Nov 20, 2021 Nov 20, 2021

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I didn't realize I was in over my head when I started doing screen printing, it is a lot. But, I am determined to get a handle on this. I actually understood everything you said.  Because I've never printed a gradient before, I just don't know what it's going to look like. I didn't even think about photoshop.  It makes sense now. Essentially, as you said it's only 3 colors. 

 

However, If I am printing spot colors, how does CMYK channels help me? What would I do? 

 

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Mentor ,
Nov 20, 2021 Nov 20, 2021

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Followup.  Question number 2.  That design appears to have been already printed ( see halftone dots in Blues ).  In order to get the White, you need to do either a flash or a flood using White undercolor.  So, the actual inks you use to print the shirt will probably be three: 1. White, 1. Black, 1. Blue.  "Lady Wolves" lettering has a blue gradient inside it.  "Basketball" has another blue gradient.  There are other methods of printing, such as inkjet or thermal transfer which may be easier.

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Explorer ,
Nov 21, 2021 Nov 21, 2021

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This shirt is only 2 color blue and white, of course with the gradient. The dots you see are a swatch I used from Adobe Illustrator, and those dots are black.

So my question is, will I have to cut the dots out first, because at this point that is the only work around I can think of?  Then proceed to doing the steps you told me on the cyan channel?

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Mentor ,
Nov 21, 2021 Nov 21, 2021

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If the garment is Black, then yes, you would have to knock out everything that is Black so the shirt shows through.  Obviously, if the shirt is dark Gray, and you want the dots "Black", then you would need to create a channel for the Black only.  So, first you have to convert your artwork to CMYK, either in Illustrator or Photoshop.  In Photoshop, when the file is CMYK, you split the Channels so you get 4 Grayscale separations.  You can duplicate one of the channels and invert it for the White.  Also, you can name the channel(s) anything you want using Plastisol reference color names.  Or, leave them CMYKW and assign each on press a particular Plastisol ink.  The artwork you sent as a sample looks very rough.  Is that a screen shot or a digital camera pic?

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Explorer ,
Nov 21, 2021 Nov 21, 2021

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yes that was sent via phone screen, the actual artwork is at my job. 

 

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Mentor ,
Nov 21, 2021 Nov 21, 2021

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Another important consideration is moire pattern in the gradients.  To minimize this, you would assign an angle when creating the 1-bit halftone screen in Photoshop.  There is a way to determine the angle based on the mesh of the silk screen you plan on using for the printing.  It could be 75 degrees, 15 or 0 degrees.  In fact, you may want to do a series of angles, such as 90, 45, 75, 15, 0, etc., print films say around 6" x 6" of each and place them on top of a silk screen and see which combinations produce the least amount of moire.  On top of that, you have the shirt's sewing pattern that affects the screening, too.

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Explorer ,
Nov 21, 2021 Nov 21, 2021

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ok i will use that information at work tomorrow and see how that works out, thanks for all your advice, very much appreciated. 

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Mentor ,
Nov 21, 2021 Nov 21, 2021

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One more thing.  The output resolution I mentioned earlier is 2740ppi.  You will get a smoother dot if you use 5480ppi.  And, in order to generate a dot large enough to image on a silk screen mesh, 35lines per inch is a good screen frequency.  Sorry, I wasn't sure based on your initial post, that you were up to speed, sounds like you are.  Feel free to post any more questions you might have as you proceed.

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Explorer ,
Nov 21, 2021 Nov 21, 2021

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thank you.

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