Thanks!!Yes it is a 6 colors design.Like Narfcake mentioned it, the number of colors is no more a problem,you can go until 18 .When designs are on black background it still need to be halftoned .
You’ll find here a forum post showing how to prepare files for shirtwoot
It doesn’t show how to halftone a document.
Try this exercise:open photoshop,create a new document 15X18 inches with 300 dpi definition.
Open a black and white document,copy it and paste it in your new 15X18 in,resize it if needed.
Now go on the image tab,select mode bitmap.A window will appear where you can choose the definition(it will be 300 dpi by default cause your document is 300 dpi).Set the method to halftone screen.Click ok.Next window will allow you to select the number of lines per inches.Set it up at 30 or 35-select an angle for your halftoning,set it up to 22,5°(looks it gives better results for printing)-Then pick the shape for your lines_You have some options but on shirtwoot lines are prefered.Click ok et voilà!!!you’ve got an halftoned document.Go back to the image tab,select mode grayscale,click ok.