If you put more pressure on the back, it permits the coater to cut more. If you put more pressure on the front, it will influence how much emulsion is pushed through the mesh and how much is cut. Insider Tip : Ryonet offers two types of scoop coaters —a standard coater and a Monster Max. Use whatever coater works best for you. The information shared here works for both scoop coaters. You can coat a screen in two ways.
One way is to hold the screen in one hand and use the other hand to apply the emulsion via the scoop coater. In this version, use even pressure on the front and back of the scoop coater. You will start the screen at an angle and as you bring the scoop coater up the screen, you will slowly straighten the screen until it's upright when you finish the emulsion application.
On the side that touches the t-shirt, apply two coats of emulsion. On the squeegee side, apply one coat. You'll know if you coated a screen beautifully if the glisten effect happens. The glisten effect is when you hold your screen up to a light and it reflects, no dull areas exist.
The glisten means the emulsion on top and bottom of the threads have fully encapsulated the threads. It's important that the emulsion is wrapped around the threads because that's how it holds onto the screen.
When you're done, put the screen in your drying rack. The picture opposite shows how the air bubbles have been trapped on the 'lee' of each fibre during coating. This will create a weak area that is likely to pinhole on long runs. The number of coats you apply and the way you coat them is the best way to control the stencil Rz and EOM.
For most screen printing applications the objective is to produce a screen that has a thin, flat stencil surface on the print side, with just a thin, fully cured layer of emulsion on the squeegee side.
Stencil build comes primarily from applying multiple wet coats from the squeegee side, whilst stencil smoothness comes from applying thin, face-coats of emulsion to the print side. Once the mesh is correctly filled the squeegee side will look glossy. If the mesh is not filled with the base coat, subsequent squeegee side coats can entrain air. Entrained air in the coating will make the stencil weak and prone to pinholing during printing. This pushes the wet emulsion back through the mesh to the print side, leaving only a thin, sealing layer on the squeegee side.
There are obviously many variations to this theme depending on frame size, mesh count, image requirements etc. All emulsions lose volume during drying as the water evaporates and consequently they shrink back around the mesh fibres to leave an uneven surface. Face-coating is used to fill in these hollows in the uneven emulsion surface on the print side to create a flat stencil surface low Rz which minimises sawtoothing during printing.
Face-coating can only be applied to screens that have already been fully dried. Typically two face-coats are applied and then the screen is dried again. If an even lower Rz is required, then additional face-coats can be applied. The two pictures opposite, show the importance of a flat stencil surface low Rz in producing good print quality. In these schematics, the emulsion is shown as pink, the mesh as yellow and the ink as blue.
The ink floods out under the rough stencil surface high Rz in the picture on the left, however the ink cannot flood out under the flat surface low Rz in the right hand picture giving a high quality print.
I spoke to screen printing experts and got some words of wisdom to help beginners like you pull through these stressful times. Hopefully these common screen printing emulsion FAQs will help you avoid messing up in the very near future. A diazo emulsion, which you need to add a water resistant sensitizer to the mix, or a water resistant dual-cure emulsion.
I would go with the diazo emulsion which is cheaper but will react slower, increasing your exposure times. The dual-cure emulsion, which is a combination of diazo and SBQ-based emulsion, cures faster and creates a thicker stencil. For starters, use these coating combos for your starting point:. You should remember that nobody gets it right the first time. Not even the experts.
I also suggest using a smooth rounded edge scoop coater on these screens instead of the sharp edge. Most manufacturers suggest a good 24 hours for a completely dried screen. But I know printers who wait only 30 minutes before moving on to exposure. They have the perfect setup for quick drying which are. I personally keep two fans running in my darkroom at all times. But make sure your area is clean because sand, dust and dirt can circulate in the air and get stuck on wet coated screens. This can cause blockages in the emulsion once it hardens.
Ideal, but not necessary. Many printers work in a room or basement with minimal to zero sunlight and use indoor lighting such as a fluorescent lamp or a yellow bug light. Regular fluorescent room lights are fine to work under. Nope, emulsion coated screens can last a few weeks with proper storage conditions. During drying the liquid evaporates out leaving a solid coating. This will then form your stencil once exposed.
Getting a nice smooth even coat of photo emulsion on your screen is essential for getting a good exposure and durable stencil.
Read: Screen preparation for Photo Emulsion. Get some emulsion: Hunt the Moon Photo Emulsion. Generally we recommend two coats of emulsion on the printside and one on the squeegee side.
On higher mesh counts you can go to one coat each side to make lighter prints. More on that soon. Fill your scoop coater just over half full. Too much it will spill out of the sides. Not enough and the coat will be patchy. Make your screen secure, we have used a block of wood to push against. Its easier like this as you will have more control with the scoop coater.
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