How to Guide - Mesh Preparation for Screen films
Mesh preparation is the easiest, cheapest and quickest way to improve screen life. This useful How to Guide will show you the best way to maximise stencil adhesion to a mesh which will save you time and money by not having to remake screens that have broken down on the press.
The importance of mesh preparation
Polyester mesh is the most commonly used mesh today because it is resistant to most screen chemicals and also it doesn’t absorb water and change tension during use. However, the down side is that untreated fibres of a Polyester mesh also have a very smooth hydrophobic surface. Inks and solvents then deposit greasy residues to this surface, so you can see that trying to get a water based stencil to adhere is very difficult!
The key to overcoming this problem is effective mesh preparation to help the stencil adhere better to the surface.
What should a prepared screen look like?
Luckily that's easy to see. A well prepared screen should be able to hold an even film of water as seen in the picture opposite, where the right hand side was prepared with Universal Mesh Prep. A quick and simple test can tell you straight away how well prepared your screens are - we've called it the Mesh Prep Challenge.
The Mesh Prep Challenge
This is a simple 3 step test, that will very quickly demonstrate just how well prepared your screens are.
- Desgrease half of your screen as usual with your mesh preparation
- Rinse it with a water spray
- Look at how much water it holds
Why not take a look at how well Universal Mesh Prep handled the challenge and compare it to your prodcut.
Degreaser or mesh wetting agent?
MacDermid Autotype offers two types of degreaser (i) Auto Degreaser Concentrate and (ii) Universal Mesh Prep. The Auto Degreaser Concentrate range is diluted with water prior to use, so 1 litre of Concentrate can make up to 50 litres of degreaser solution.
The concentrates work brilliantly for PLUS direct emulsions, however if you are using Capillex screen film then we recommend Universal Mesh Prep, which is a combined degreaser and mesh wetting agent. This helps the mesh to hold as much water as possible which is the key to applying Capillex successfully.
Top tip: to save time always degrease the mesh after decoating the previous stencil and then store the screens covered so they do not become contaminated again.
The Brush Pump is an excellent tool for use with the Auto Degreaser Concentrate. Add 1 litre of the 1:25 product to the 25 litre drum and then top up with water. Simply moving the brush up and down the screen will activate the syphon pump and apply just the right amount of the degreaser solution to the mesh.
No air or electrical supply is needed to operate the Brush Pump so installation takes seconds.
If you are using Capillex or an indirect stencil film such as Five Star, then it is important to abrade/roughen the mesh as well as degreasing it. This will ‘key’ the smooth mesh fibres allowing the stencil to adhere better. The picture opposite shows the level of micro-abrasion that ‘keys’ the surface without damaging the fibres
Top tip: Abrade all new screens and after every fifth stencil to get the best results.
This ready to use micro-abrading liquid is simply applied to both sides of the wet screen with the Autotype Brush for a perfect result. The Autotype Brush has soft, chemically resistant fibres to give the maximum effect without damaging the mesh. Can be used with Auto Degreaser Concentrate solution, Universal Mesh Prep and Autoprep gel.