Hello from South Australia. I used to post on here years ago, but stopped when I stopped printing. Was a textile printer for 5 or so years, but quit when I got sick of working for a-holes that either had no idea about printing, or knew too much and you were never good enough.
Long story short, after a few years hiatus where I've been concentrating on bikes, bands and house renovations, I've pulled all my screenprinting stuff out of storage and have finally set it up. It's inspired me to print a small zine with photos my friends and I have taken as halftone single colour prints. I'm using waterbased ink.
I have managed to remember pretty much everything, and have exposed the screens. The halftone has turned out fine, but I'm having some issues.
1. My screens are breaking down after a couple of washes. This isn't too concerning right now, but I'm not sure it's the emulsion, the exposure time (which is quite long because of my light source), or if I should expose my screens after I've washed the image out. The emulsion is from a friend who runs a printing place, but he mainly uses plastisol. He does use this emulsion for waterbased and solvent as well though.
2. The stock I have been using for test prints has been warping / wrinkling when printed. I plan to print on both sides of the paper as well. I obviously don't want to go too thick, but I've gone up to 120gsm (32lb I think) and it's still wrinkling after being printed. Any suggestions for thickness? I'm considering going up to 200gsm (70lb?) for the pages and 300gsm (110lb?) for the cover. I'm using a 98t screen (240?) and the halftone is 45dpi. Could I be pushing too much ink though. I'm doing a single pull with a flood coat after each pull, and am trying to not pull to heavily.
Thanks for any help and suggestions, and sorry for any conversion problems with the paper and screens, Australia and the US is quite different.
How are you exposing your screen? Longer exposure time will help against break down but also you may lose detail. What emulsion you using? You can post expose your screen. We do double the time for each side. Also you could use a hardener. We found it works best if you put it on a dry screen after exposure process. We also found that allowing 24 hours or more will form a better cross link bond. Do not use the super hardener otherwise you will not be able to wash out your emulsion.
Paper you can get away with 55 lbs cover. I know a lot of people like 80lb or 100lb. Make sure to pre-rack your paper. 2 days a head. Act like you printed it and rack it up this helps to adjust to temp, humidity and the environment. I usually will try to print all the colors in one day. This helps to fight against shrinking of the paper. As water base ink cures it changes the paper. Print smallest layers 1st to largest.
Screen is being exposed on an old light table with fluoro lights. I face the the screen down towards the light on top of the transparencies, with weight on the squeegee side of the screen. Exposure time is 30 mins. Not sure of the emulsion, I'll find out. I might try and expose the screen for another 30 after I wash it out. I'll also look at investing in some higher wattage bulbs this weekend.
I'll try pre-rack the paper as well. I'm only doing 10-20 prints a time, all single colour, so I'm just laying them out on a table to dry.
Pre racking shouldn't matter if you are doing just one color. I would see if you can get unfiltered black lights in your light table. Or even better see if you can find a nice shop that would expose and coat your screens.
Well... I do have a shop that I could get to expose, coat and even print for me, but it's my friends proper business and I don't really like having to impose on him to do stuff like this, and it's also nice to be self-sufficient. I have everything at home, have printed for a living (mainly textile), printed using my home set up and even am "qualified" screen printer (whatever that means, but I have a certificate!). It's just little thing that stump me like printing on thinner stock, which is newish to me.