# Screen printing on Coroplast...Newbie What am I doing wrong?



## BrandywineValley (Oct 18, 2008)

AHHHHHHHHH I've never screen printed anything and need help! I figured I would start with coroplast signs because I know a lot of people who need them and then move onto t-shirts when I expand. Now I am thinking I am crazy!

I've tried using a 230 and 280 mesh aluminum screen on my vastex press and can't get a print to work! I didn't use emulsion, instead I printed out the design on my vinyl plotter and then painted the screen with speedball screen filler. It worked perfectly until I tried to print. I'm using NazDar 7900 black straight out of the can.

I've attached pictures.


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## TshirtGuru (Jul 9, 2008)

Are you printing with the direction of the flutes?


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## BrandywineValley (Oct 18, 2008)

TshirtGuru said:


> Are you printing with the direction of the flutes?


Yes. Should I print the other way?


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## macmiller (Jul 23, 2007)

it looks to me to be either, not enough off contact, no spray tack or anything to hold the sign down and not enough pressure on the squeegee. it may be all three things. 

i see a couple of "spiderwebs" are you using thinner? naz dar re-180 or the retarder type (re-??) is what you need

vinyl works great for about 20 prints, but the ink will eat it up after that.


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## BrandywineValley (Oct 18, 2008)

macmiller said:


> it looks to me to be either, not enough off contact, no spray tack or anything to hold the sign down and not enough pressure on the squeegee. it may be all three things.


I think it may be the off contact. I'm using a vacuum pallet and pressing down pretty hard on the squeegee.



macmiller said:


> i see a couple of "spiderwebs" are you using thinner? naz dar re-180 or the retarder type (re-??) is what you need


No thinner. I am going to get some first thing on Monday.



macmiller said:


> vinyl works great for about 20 prints, but the ink will eat it up after that.


I used straight vinyl for my first try and it didn't last very long. Thats when I decided to use the speedball screen block.

Should I print with the flutes or against?

Henry


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## pixelwhisperer (Jul 23, 2008)

Ok coroplast Is way harder than shirts because plastisol doesn't dry in the screen In fact you could come back a year later and the plastisol still wouldn't be dry. Nazdar Ink on the other hand is just solvent based paint. If you have ever painted a house and done the trim with oil based paint then you have experienced what happens when the paint drys on the brush. Nazdar dries even faster. I have done both types of printing many times and my two rules for coroplast are print in low humidity with cooler temps If your shop is airconditioned turn it down as low as you can. Also once you start, don't stop, print as many as you can keeping the ink moving. I also add a little thinner trying to keep a balance between getting a good dark print and getting a nice flowing consistency. Goodluck


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## frankiko (Jun 13, 2008)

coroplast is really a pain to me too...
if job is just text, just like what you have, i do vinyl.
i hope some experts here will get the time to post good methods on how to screen print on this kind of substrates.


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## mike2468 (Mar 11, 2007)

BrandywineValley said:


> I used straight vinyl for my first try and it didn't last very long. Thats when I decided to use the speedball screen block.
> Henry


What type of vinyl were you using. I put vinyl on coroplast all the time is it lasts for years outside, forever inside.

Mike


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## jsreid (Oct 10, 2008)

mike2468 said:


> What type of vinyl were you using. I put vinyl on coroplast all the time is it lasts for years outside, forever inside.
> 
> Mike


I think he was talking about using vinyl for the stencil on the screen instead of emulsion.


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## BrandywineValley (Oct 18, 2008)

jsreid said:


> I think he was talking about using vinyl for the stencil on the screen instead of emulsion.


Exactly. Although I have had some Oracal 651 lose color after being outside for a while.

Henry


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## ino (Jan 23, 2007)

From the little that I,ve learned about screen printing on coroplast, the squeege should be a hard one, and the subtrate 3" all round smaller than the screen.
Secondly, depending on the quantity needed if it would be a small number I would vinyl it, if a large number I would cut a stencil and spray paint them. just my thoughts.


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## seattleprintshop (Jan 15, 2007)

Buy a vinyl plotter like the rest of us.


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## BrandywineValley (Oct 18, 2008)

seattleprintshop said:


> Buy a vinyl plotter like the rest of us.


I have a plotter. When you need to make a 100 signs it can be a little bit of a pain to do that with vinyl. Thats why I got a screen printer. 

I adjusted the off-contact and that seemed to do the trick. I am going to pick up some retarder/thinner tomorrow and see how that goes.

Thanks for all of the help!!

Henry


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## screenprinter1 (Jan 5, 2008)

OK, where do I start? I've been printing coroplast for many years. I don't do it anymore, because not only does it kill brain cells, but well,... it kills brain cells. Here are the critical point of printing coroplast:

1. As you guys have already mentioned, your off contact is critical! You need to have enough to allow the screen to pull away from the mesh as you print, but not too much or you won't be able to get enough pressure.

2. Buy a whole case of screen opener. Screen opener will also kill your brain, but it is absolutely the only way to print with air dry ink. It's better than thinner because you can flood your screen, and lightly spray your ink to loosen it up as you print. It is also great to clean out your screen at the end of the day.

3. Use emulsion, your screen will last longer! Blockout is not tough enough.

4. Don't use tape to fill pinholes. Air dry inks eat through tape adhesive and it will only cause you problems later down the road. Use emulsion.

5. When you burn your screens, make sure that you position your images so that you don't have to move your template.

6. 155 to 195 mesh screens! I have had many suppliers recomend over 250 mesh, and you will fight it just like the guy on this post! Your ink is thin, but not that thin, and you will not have to work so hard if you at least use a 195 mesh. I don't think suppliers have ever really tried to manually print using a 250 mesh screen. 250 works great for automated printing machines, but not so great for us manual guys.

7. One post on this forum recomended using a hard squeegee. DO NOT USE A HARD SQUEEGEE! Use a 60 durometer squeegee which is the softest that I have in the shop.

8. Most of you do not grab your squeegees properly. You need to grab the sqeegee with the center of your palms directly in the corner of the squeegee, with your thumb on the back and your other fingers on the front. This gives you even preassure all across the squeegee blade, which is very critical when printing plastic. If you have a large image that covers almost the entire screen, you may need to grab another person and two man your squeegee. 

9. As you pull the sqeegee, watch your mesh you will see when you have missed areas. If you miss an area, do not flood the screen again, just try to dry print it.

10. You only want to print the image once if possible. You print pulling toward yourself, then lift the screen slightly and flood the screen pushing back away from yourself.

11. Always make sure that before you pull the squeegee that you have some ink in front of the sqeegee.

12. Once you start printing, make sure you keep your screen flooded. It will allow you to keep printing for long periods of time. If you need to clean your screen, print a junker and then don't flood the screen.

13. Once you start, don't stop! Give yourself enough time do an entire color all at once. You can do both sides of the sign if you remember where you put your first print and start with it. 

14. If your image bleeds a little bit, instead of trying to clean the back of the screen, just take some junkers and print three or four. That will usually take care of the problem, and you won't risk spreading a thin layer of wet ink all over the back of your screen. 

15. If your image bleeds severly, and you need to clean the back of the screen, then print the image one more time on a junker, but this time don't flood. Take your screen-opener lightly spray it on the bakc of the screen. Wipe first on the bottom of the screen, then the top, then spray your cotton rag and do the bottom again. You will want to print a junker just to be sure.

16. When printing, watch the ink behind your sqeegee. If you are dragging little streams of ink behind the sqeegee that is bad. Unlike printing textiles (for the most part) this will put more ink in those areas and will show up on your sign. You want to scrape the ink nice and clean. If you are not applying consistent preassure, then you will see a "stuttering" effect both in your screen and in your print. This shows up as light lines in your print.

17. I like to reclaim my screens immediately after finishing a job. This way I know that I am getting all of the ink out of the screen. You absolutely need to clean your squeegee with screen opener and get all of the ink out of everywhere, especially in the corners.

18. Use a chemical mask! Don't kill brain cells.

Let me know if you are having any other problems, or if you have any other questions.


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## frankiko (Jun 13, 2008)

Thanks, Matt. Will surely try your method and configurations.


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## ino (Jan 23, 2007)

Thanks Matt, very instructive and your advice much appreciated, One more question if I may ask.
Could I thin the ink enough to be able to spray paint it with stencils.


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## screenprinter1 (Jan 5, 2008)

I just reread what I wrote, and sorry everyone that I didn't put those steps in a better order.


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## screenprinter1 (Jan 5, 2008)

ino said:


> Thanks Matt, very instructive and your advice much appreciated, One more question if I may ask.
> Could I thin the ink enough to be able to spray paint it with stencils.


You could try, but you will get much more consistent prints by screen-printing it (if you do it right). If you water down your inks too much, they will lose their opacity, and you also have to worry about the ink running or getting under your stencil. 

Out of curiosity, why would you want to spray if you can screen-print them?


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## screenprinter1 (Jan 5, 2008)

It seems to me that doing multiple colors by spraying and stenciling would much more difficult. Also, you can't do consistent halftones by spraying. If you're not doing either of those things, then spraying could be a viable option. 

You should definitely use a mask if you are spraying or printing, this stuff is nasty. I worked for a sign shop for about a year and had to drive down a windy canyon road every day to get home. My wife would call me as I was coming home after printing signs, and there were times that she thought I wasn't going to make it. The fumes used to give me bad headaches too.


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## ino (Jan 23, 2007)

Hi Matt, I just asked out of curiosity.I realize that screen printing could be more appropriate than spray-painting.
However my line of thought is, no printing of transfers,no exposure problems,no emulsions,no screen size or mesh problems,no clogging of inks,no squeege problems,no degreasing etc. Just my thoughts as a newbie.

As for the pungent fumes,I most definitely agree with you for the use of a good quality mask and an extractor fan.


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## JOAT (Nov 12, 2008)

I am so interested in offering screen printed signs. I understand the fumes risk we have great venalation and masks... My question is what mesh is most commonly used, I did read the post but it seemed like there were 2 numbers typed in 155-195. I have a thinner but which paint is strongly suggested (where to get it)


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## ino (Jan 23, 2007)

Most ink manufacturers would have a suitable ink for coroplast. Maybe you could check up nazdar, see where their distributors are located, and go from there.


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## tgraphix (Apr 3, 2009)

Great instructions for printing on coroplast. I too have been fighting the stuff to try and get consistent results. Would you mind to share the name/type of ink you found to be most effective please?


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## acetransco (Jan 2, 2007)

You need To Check with Nazdar, to make sure you are using the right ink for coroplast, sometimes you need to add a bonding agent, to make sure the ink adheres to the substrate, just because you can print it, and it looks good, does not mean that it won't scrap off. I think that you also need a higher mesh screen, and either a thinner, or a retarter to slow the ink's drying time. Nazdar # is
800-729-9942, they should have the answers. Air dry is one way to print the signs, we use UV inks, and a UV dryer, it's like printing plastisol, the ink will not dry in the screen, and as soon as we print one side, we can flip them over and do the other side without doing 2 setups
We offer contract printing.
Regards, David


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## printing40years (Dec 27, 2008)

Stop polluting the air and buy a UV curing unit like we all do here in California. The ink never dries in the screen like plastisol and there's no smell. The ink prints nicely and lasts as long as the Coroplast sign does. I use Sericol Polydyne PN series. www.sericol.com


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## tgraphix (Apr 3, 2009)

Thanks for the advice, I will give the UV inks a shot....I sure like the "prints like plastisol" part of your reply!

tom


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## tgraphix (Apr 3, 2009)

Thanks for your help in identifying a brand/type of ink to try on the coroplast. I will give the UV inks a try.

tom


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## printing40years (Dec 27, 2008)

Well first look into the cost of a conveyorized UV curing unit. It may bee too much. They are made by M & R Equipment in Chicago and American Ultraviolet


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## ino (Jan 23, 2007)

A UV curing unit will cost an arm and a leg. A good extractor fan is useful to clear the air.
To save on space you could stack up the boards by putting small dividers between them.


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## printing40years (Dec 27, 2008)

Every screenprinter in California has one or more UV curing units.


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## privatejet1 (Nov 27, 2007)

I print coraplast signs with Nazdar GV Series inks.
Nazdar will tell you that you cant use that ink on coraplast.
But my trick is to print them and the shake can some clear 
coat on them and they last forever,well,as long as someone
would use the sign.
I print them on 6 color press and use my spot dyer to do
more than one color on the sign then run them through conveyor
dryer with the setting low heat.(Just to help with drying)
Works GREAT for me.
I can print well over 100 signs and NO ink dry in the screen.
I use a 195 mesh.
I also use this ink to print bumper stickers.
Nazdar GV Series is awesome!!!!


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## tgraphix (Apr 3, 2009)

That sounds interesting and worth a try. Thanks for the info.


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## hcp482 (Feb 1, 2008)

Ideally when printing on Coroplast you want to be using UV cure inks. Or thinning down plastisol alot . UV inks where designed for this application. Also the easy fix would be your off-contact. From the images that you have it is pretty safe to say that your off-contact needs adjusting. If you can afford


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## printing40years (Dec 27, 2008)

Once they go through the UV curing unit they can bestacked as high as you want. They are completely dry by a chemical recation to the UV lightwaves. You don't need to worry about them sticking together and you dont have any solvent fumes to hurt your lungs and sinuses. There are no masks out there that will protect you from Nazdar GV vinyl ink fumes and the solvents used to clean them up afterwards. Life is too short as it is. Be safe.


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## tpitman (Jul 30, 2007)

I use Nazdar's Corogloss Inks. Thin it 15% by weight with Nazdar's Thinner/Retarder - this is key. Get your work area set up with your stack of signs and where you're going to let them dry. I mix my ink up in paper cups so it's one less thing to clean when I'm done. Have all your clean-up stuff handy before you start, too. I use Nazdar's Graphic screen wash to clean the ink out of the screens and off the squeegie, then hustle it over to the sink and use my standard ink degradent and water. You need to use an emulsion that is solvent-resistant. Since I do shirts also, I've started using Ulano's QX-1. Reclaims beautifully.
As others have mentioned, you have to keep your stencil flooded and keep working. 3 to 4 signs a minute, and clean up as soon as you're done. I find if I'm doing, say, 50, that I can start backing up the first ones as soon as the first side of the last one is printed. I ususally let them stand overnight to make sure they're completely dry. I have a respirator I use most of the time, but I print my coroplast signs by my rollup door with a fan drawing the fumes outside, anyway, and really don't notice the smell.


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## tgraphix (Apr 3, 2009)

Thanks for your help. I have been using the ulanao QX-1 and have been very pleased with it as well. When printing on the coroplast, are you able to do fine detail...do you have a problem with ink stringing as you lift the screen or does the thinning help solve that problem.

tom


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## Tallflags (Aug 25, 2009)

that was probably the most informative post i have seen on coroplast screen printing EVER. I registered just to thank you!... But also to add my 2 cents... I am using a 160 mesh with Nazdar 9700 series with a retarder about 15-20% thinned or to your liking... if you DO NOT thin it YOU WILL get spiderwebs and also IT WILL DRY UP in the screen... so do yourself a favor have alot of screen opener and alot of coroplast ready to be printed and dont stop once you start, they seem to be drying at about a rate of 5-6 mins in a 80 degree room with relatively low humidity (18x24 inch sign) i just hang these using clothes pins and a nylon thread running across the top of the room they dont run or drip and dry fairly fast... this method takes alot less space because you really dont tend to use the ceiling for anything and also this allows for the smell that everyone seems to complain about to dissipate towards the top of the room and be sucked out with vents... although that nail idea was pretty good but i still think it takes too much space that could be used for something else... oh yeah and WEAR GLOVES! the ink is really hard to get off of your hands!

i hope this helps...


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## amp267 (Oct 11, 2006)

my secret to printing coroplast is out sourcing. i can almost get them for the price it would cost me to print them, thats taking time into consideration. if its for a good quantity i out source, if its small i use cut, or printed vinyl. i guess someone has to print them, so i cant knock you for trying.


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## myoung4828 (Apr 24, 2010)

i use 7900 everyday and print on coroplast everyday.
it must be thinned, i use the thinner retarder 9050
also, printing on coroplast requires off contact


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## Neon Bible (Mar 24, 2010)

I agree with amp its just more effective to out source. For smaller orders try signs365 or for screen printing bdgraphicsinc.


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## Rebelgraphics (Dec 10, 2015)

too much of a headache, I outsource all my screenprinted coroplast jobs


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