"Napkins for all occasions""

www.personalised-napkins.com

Screen Printing

History and OverviewPrinting a balloon by hand

I began screenprinting in 1990 because I wanted to print onto latex balloons. Having imported a machine from the U.S. I needed to make screens for it. It took about a year to get reasonable quality. You can learn from books or videos but they can be very technical and not answer the basic questions that you need answered. There are so many little practical tricks that can give you a perfect screen every time. This is especially important when you have an urgent order to get out! There are so many choices when you are looking for supplies and the manufacturers and ink manufacturers know nothing about printing onto balloons (or paper napkins for that matter.)

Which kind of screen mesh to specify for your screens, which emulsion to use to make your stencils, which ink to use? I will answer these questions as well as where to buy printing machines and the ink and screenprinting materials. How long to expose the screen, how to get a perfect screen without blockages, how to get the ink to dry properly.

We make up our screens by coating the mesh with a liquid photo emulsion and letting it dry. Then we attach film positives to it which carry the artwork for the orders and then expose it to UV light. The screen is washed out with water which reveals the images. Clear areas on the screen where the dark part of the film was will allow the ink through during printing. Topics on these sheets: Overview of balloon and serviette printing. Basics of screenprinting. Making up a screen step by step. Basics of printing on balloons, step by step. Same for Napkins.  Where to buy machines. Types of machine. Where to buy ink, screenprinting materials, balloons, napkins.  Types of customers.

I ended up designing and making our own semi-automatic balloon printer. So I learnt about the pneumatics systems (compressed air controlled by valves & timers) that power the machines. Our own balloon printing machine uses compressed air so it is not directly connected to mains electricity. The same is true for our semi-auto napkin printer which we imported from the USA.  At present we are not making and selling our own semi-auto balloon printing machines because I think there is much more demand for a very cheap manual system. We are developing this at the moment.

There are three main kinds of printing machine or “screen press” as a screenprinting machine is called.

  1. Manual printing is where everything is done by hand: placing the item to be printed, setting the screen in place ready to print and making the print using a handheld squeegee. Most of the T-shirt presses you see for sale are manual.
  2. Semi-automatic is where the item to be printed is put in place by hand, and then a button is pressed and the machine does all the rest. The printed item is removed by hand after printing. Also usually the ink is put onto the screen by hand when needed, for example our napkin machine normally needs more ink after each 30 napkins printed.
  3. Fully automatic where the material to be printed is fed in automatically and also stacked or bagged after printing. For napkins this would be done using a roll of paper, they are cut and folded after printing. For balloons there are clever devices that place each balloon on a nozzle ready to be inflated and printed.

The beauty of screenprinting is that once you learn how to make the screens they can print onto almost any flat surface. You just need the right ink for each kind of material (or “substrate” ) you are printing.  Balloon ink has to be stretchy and also needs to chemically bond with the latex of the balloons so it does not peel or rub off.  The trick that people do not know about printing balloons is that they are blown up before printing.  For our manual process we supply a box which holds the inflated balloon in place for printing.  Then the screen is pressed down on top, ink is applied and using a hand held rubber squeegee the balloon is printed. Then it is allowed to dry for a few seconds before deflation. Application of mild heat from a hairdryer shrinks the balloons back to their original shape.

Making up a screen:

1) the most basic method is to block out part of the screen, just leaving the areas clear where you want the ink to go. You can do this by cutting out a stencil from a plastic sheet and applying it to the underneath of the screen. An easier way is to use the green screen filler which is a liquid you can paint on. It dries on the screen forming an ink-proof layer on the screen.

2) using a wax crayon or special drawing fluid (not supplied) you can write or draw directly on the screen. Then the screen is coated with screen filler. When this dries the crayon or drawing fluid can be removed with methylated spirit leaving the image clear to print.

3) light sensitive emulsion (diazo). This is what we use for text, logos and photographs. The screen is coated with emulsion and allowed to dry. It is then sensitive to light so must be kept away from direct sunshine or bright artificial light.  We then print out a film positive from our computer. This is a black image on a transparent sheet. This is stuck to the screen and exposed to UV light under a sheet of glass which holds it in close contact with the screen. Then the screen is washed with water and the unexposed areas wash away leaving the image. The light hardens the emulsion so it does not wash away in the areas which are not covered by the black part of the image.