Coating screens

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the meshman
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Coating screens

Post by the meshman »

I am using SBQ 500 Photopolymer emulsion and burning the screens with 4 Fluorescent bulbs about 6 inches from the screen. Does anyone have any recommendations on how to coat my screens (i.e. 110, 158 mesh counts). Should I do 2 outside and 1 inside? Any ideas would help. Thanks.
broham23
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Re: Coating screens

Post by broham23 »

It really depends on a few different factors, for example the condition of the screen, how thick or runny your emulsion is, and how much emulsion you pour into your coating trough. The main problem you'll encounter if you coat with too little emulsion is of course pinholes. Generally speaking, the thinner or runnier the emulsion, the less number of passes you'll need on either side of the screen. Also, the lower the mesh count, the more passes you'll need to sort of "fill in" the larger holes in the mesh. On really tight mesh, like 230 or above, just two passes or so on either side should do you. Conversely, if coating an 81 or 110 screen, I'd typically put 4 passes on the inside (squeegee side) followed by 4 on the other side (shirt side) and finish off with 3 or 4 once again on the squeegee side, and I'd dry it squeegee side up so the emulsion doesn't have to seep back through the mesh as it dries. It just kind of hangs on the underside of the screen and dries nice and smooth and flat. However, this is what needs to be done at my shop with my emulsion (a mix of ulano 569 and ulano tz) on my screens, and your equipment may require a slightly different approach.

So for your 110 screen I'd put 3 or 4 passes on either side as I described above, (in three steps, squeegee side, shirt side, squeegee side) and then dry it squeegee side up. Put something under the edges of the frame so it doesn't stick to anything you've set it on, like little pieces of wood or cardboard or something.

For your 158 screen, do the same but omit the 3rd step. Put 2 or 3 passes on the squeegee side, and 2 or 3 on the shirt side and dry it squeegee side down instead of up.

Before you burn, hold it up the a light briefly to check for pinholes. If there are any, it's okay--just put another pass over top of the dried emulsion, one pass per side and dry it again. This will fill in all the pinholes.
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