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Kiwo "Thick EOM" process
When extremely thick emulsion build-ups are needed (over 700 microns).Note: The rod or scraper needs to span the dam so that the ends of the rod or scraper rest on the dam and not in the open area.(and when production of the screens are not needed in a relative hurry)
1. After the wet-on-wet base coat is dry, secure a dam device with two sided tape. The open area of the dam should be at least 2 ½ inches wider on all sides to the image area. The tape should be along all four inner sides of the dam.
The dam can be as thick as needed and can be made out of coated card stock, polyester or non-corrosive metal.
The following diagram illustrates placement of the dam device on the screen before pouring the emulsion into the dam.
Top & side view of screen with dam device.
2. With the screen in a level and horiztonal postion, pour emulsion into the dam, covering the entire open area with emulsion.
3. Allow the emulsion to flow evenly into the open area. This takes about 1 minute.
4. Place a (stainless steel or glass) rod or scraper (such as a coating trough edge) on one end of the dam and SLOWLY pull the rod or scraper across the open area of the dam. This action removes the excess emulsion and leaves a coating as thick as the dam. Return excess emulsion to container.
Note: With practice, emulsion can be poured into the dam without scraping. The flow of the emulsion results in an even coating.
5. With the dam still in place, dry the screen in a horizontal position with the SQUEEGEE SIDE DOWN (See ‘Drying Face Coat: 6.5’ for more details). The screen needs to dry in a completely flat and LEVEL position, or the emulsion could flow to one side or the other of the dam resulting in an uneven coating.6. Measure the emulsion over mesh (EOM) with a thickness gauge, such as the KIWO STENCIL THICKNESS GAUGE.
7. The coating will shrink approximately 65%, so a repeated pour of the emulsion may be nesseccary.
Advantages:
Thick emulsion over mesh can be achieved with one wet-on-wet base coat process and one pouring process.Disadvantages:Various thicknesses of the dam determines the resulting EOM thickness. The user can estimate the thickness needed.
This process can be somewhat inconsistant depending on the skill of the screen maker to pull a rod or scraper across the screen or to pour the same amount of emulsion into the dam.The drying of the face coat takes at least 24 hours in elevated temperature with low humidity (See ‘ Drying the FACE Coats: 6.5’ for more details).
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Thin Stencils or without shims || Medium Thickness Stencils (50-800 microns) || EOM's greater than 700 microns |
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