There are some items that are easier to print than expected if you understand the potential problems before you start. Umbrellas are really easy once you have the proper items in place and work out the procedures. The first thing to realize is umbrellas are usually made of nylon. When nylon is heated, it shrinks, so pre-shrinking the nylon is a must for multicolor printing. Umbrellas are also waterproof. The reality is, you are not going to wash your umbrella, you are only going to get it wet, so getting the ink to adhere to it is not as difficult as a nylon jacket which will probably be washed.
Nylon does not absorb, so whether you are printing on a light color or dark doesn't matter, the ink will stay on top and look vibrant as long as you started with an opaque ink.
I am a fan of butt registration. If you set-up your artwork with a trap, you chance getting secondary colors you may not want. In order to work with a butt register, you will have to be very committed to procedures, which I will go through shortly. If you feel you need to have an underlay for the image you are going to print, make sure you have choked the underlay very slightly, maybe a half a point.
I am a fan of retensionable frames because of the control I get from them. In this case, control is paramount. I like to use 230 mesh with 40 N/cm. With a multicolor design, make sure all of the screens have been tensioned and retensioned the same number of times in order to hold registration. Using rigid frames is much more difficult because if there is any movement of the mesh, the print will smear since the nylon does not absorb.
A two-part nylon ink is a good way to go if you do a lot of nylon printing. If not, then I would recommend using a high opacity plastisol and adding nylon catalyst to it. Most companies recommend 10%-15% catalyst by weight. I would stay around the 10% range so the ink has better opacity. The more catalyst you add, the less opaque the ink becomes.
This is where I feel most printers loose it when it comes to printing umbrellas. Many try to use a flash unit. The problem with using a flash is heating up too large an area and not having enough control. That's not to say you can't use a flash unit, but it is much more difficult. I prefer using a heat gun. By using a heat gun, I have control of the area that I will print on and not shrink the rest of the umbrella. I will also be able to determine when the ink has gelled, since it will go from being shiny to dull. Once the ink is dull, I can print the next color. Since I will only be heating the area that will get the print, it will not take very long to heat this area so production will not be too slow. Curing or fusing the finished print can be done with a heat gun, flash unit that is set further away than when printing on garments and using a heat gun to check the temperature, or, you could place a cardboard insert under the panel that has been printed and send the umbrella through your dryer. Make sure there is someone on the other end to catch the umbrellas as they come out. If using a flash unit, open the umbrella and place it on the floor so the print faces the flash unit. I would be about six inches away from the flash and using a heat gun, you would want to reach a temperature over 275 degrees F.
It would be best to make a pallet that is shaped like one of the panels of the umbrella. This will allow you to print the umbrella without opening it up completely.
Procedures and photos
|Register your screens as you would for any other job, and choose a very sharp, straight, medium durometer squeegee (70-75 durometer). Add catalyst to your ink using a scale to measure the amount, then stir the catalyst and ink together thoroughly. It is best to use the catalyzed ink within four hours. Only mix as much ink as will be needed since the unused ink will need to be thrown away.|
|Check that all the screens are registered correctly, then add ink to all of the screens. When the job is done, make sure you clean out all the ink before it sets up and ruins your screen.
Spray adhesive on the pallet and let it dry before placing the umbrella on it. Since nylon does not absorb, nor does it have much lint, you should be able to print quite a lot of umbrellas before needing to spray adhesive again. Using a liquid adhesive is still my favorite way of holding umbrellas in place and knowing that I will not get any adhesive on the underside of my umbrellas because once the liquid dries, heat will not affect it. If you use a spray and get it too hot, it could stick to the underside of the umbrella.
|Without opening the umbrella, slide it in place on the pallet.
Using a heat gun, heat the area that will be getting the print. Use the same amount of heat you would use if ink were on the umbrella and you needed to gel it. You will need to do a little testing before starting to get your timing down. Don't get too close to the umbrella with the heat gun or you'll melt the nylon.
|Flood your screen, then come down and print your first color. You should have a minor amount of off contact with your screen so the mesh peels away from the umbrella as you are printing. Use only one print stroke or you chance smearing the print.|
|Dry the print using the heat gun. You'll know it's dry when the ink turns from glossy to dull. You can gently touch the print to see if it's dry, but if it's not, you'll have a fingerprint where you touched.|
|Print the next color and dry it using the heat gun. Repeat for all remaining colors in the print.
After the last color has been printed, use the heat gun to make sure you don't smear the print getting it off of the pallet. You can use the heat gun for the finished cure or a flash unit or by sending it through your dryer after putting a cardboard insert behind the print to keep it from folding over and not getting the correct amount of heat.
The finished print!
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