Just a quick question: when i'm reclaiming my screens I have a very faint 'ghosted' image visible on the mesh. I've tried using the alcohol-type cleaning solution supplied with my inks (waterbased) but it doesn't really seem to get anything off. I think its just where the ink has coloured the mesh as opposed to 'filling' it as I seem to be able to use the screen around that ghosted image again, but am I expecting too much? Should my screens be 'as new' after reclaiming? Or will there always be some kind of staining there?
For the record, the emulsion comes off fine and i've tried cleaning the ink both before and after emulsion reclaim - neither way seems to make any difference.
I'll also add that I wash the screens down after printing, so theres no ink actually sat in the screen - this is just when I come to reclaim.
You will get some staining, even after reclaiming. It can affect the printing in theory, but the practical reality is that at low-levels it's not likely to. Once it gets bad enough you can use dehazer, but given the caustic nature of dehazer it's best to avoid using it when you don't have to.
There are two types of hazing that are common to beginning screenprinters - emulsion hazing and ink hazing.
Emulsion Hazing
The hazing caused by emulsion will exhibit a stain in the area where there was emulsion. The open areas where the ink was transfered may wash out well and leave the screen mesh its original color. The color cast left by hazing will vary in color with the emulsion being used, but generally leave the mesh a slightly darker color than the original color. If you mesh is darker in the emulsion area, you have emulsion hazing.
Emulsion hazing is most often caused by underexposed emulsion. If your emulsion is not completely polymerized (hardened) by the ultra-violet energy of the exposure unit it will not wash out completely during reclaiming. When you are developing your stencil after exposure, place a finger on the ink side of the stencil. If the stencil feels slimy or the color of the emulsion comes off - even slightly - onto your finger, you are underexposing that screen and it will not reclaim well.
A second reason for emulsion to not reclaim well is that it has been 'burned' into the mesh by the use of 'hot' chemicals. This is more prevalent on pure polymer emulsions but can happen to all emulsions. You should never use a 'hot' chemical on emulsion. A hot chemical is one that evaporates quickly such as lacquer thinner. The lacquer thinner can actually 'set' pure polymer emulsion and cause it to 'lock' up in the screen and become so hardened that it cannot be reclaimed. A little will cause the hazing to take place.
Hot chemicals can cause the polyester mesh to open up and allow the emulsion to leach into the polyester filaments similar to the ink and make the emulsion difficult to reclaim. The only way to remove this haze is to heat the polyester filament up with something like caustic soda or lye and allow the emulsion to be released from the filament.
Ink Haze
Ink haze can be caused by many reasons, but all do the same thing - cause the ink to become trapped in the polyester filament. This can be caused by the use of 'hot' chemicals, friction on the mesh, or by leaving the ink sitting on the open areas of the mesh and allowing the mesh to reach a high temperature. Sometimes the ink itself is so 'hot' that it will leach into the polyester filament on it's own.
The only cure to leach the ink out of the polyester filament is to heat the filament so it will open and cause the release of the trapped ink. This can be done with caustic soda or lye.
Be very careful when using these and other chemicals as they can cause severe injury. Wear protective eyewear designed to protect the user from splashes and fumes. Wear protective clothing that will also protect the body from these chemicals at all times.
Thats interesting, I also have a little haze where the emulsion has been.
These screens are at least a fortnight from being exposed though, even if they had been slightly underexposed then would they not have become fully exposed in those 2 weeks?
Ink 'ghosting' on screens 
Re: Ink 'ghosting' on screens 
