Emulsion Info for the Screen Printer
A technical details post
Emulsion Over Mesh or EOM is a measurement of the emulsion density on the face or substrate side of the mesh. EOM is a portion of the mesh density.
Direct/indirect and capillary movies will certainly produce the most affordable Rz numbers possible for screen stencils. High solids content emulsions and face covering (2nd or more coats of emulsion over dry very first layers) can likewise decrease your RZ measurements.
Now you can see the emulsion with a loop or microscope. Check the modifications in density, then print with this screen and check the printed outcomes.
Direct/indirect movie items need a layer of direct emulsion. One approach is to coat the screen (one stroke on each side of the screen) then position the screen (squeegee side up) on the movie (emulsion side up) and stroke the squeegee side of the screen with a low pressure stroke with a soft squeegee.
Screen printers have offered 6 kinds of photoreactive stencil products. There are 3 direct emulsion options, diazo, diazo/photopolymer (dual remedy), and SBQ-photopolymer. There are likewise 3 image reactive movie options, indirect movie, direct/indirect movie, and photoreactive capillary movies.
Capillary movies struggle with previous bad track record for delamination the existing items offered can long terms and exceptional information. Capillary movies produce the most affordable Rz numbers possible and can conserve huge quantities of screen space production time.
Indirect movie items are presensitized emulsions on movie. They are produced to expose and establish prior to they are connected to the screen mesh. Indirect movie has actually fallen out of basic usage as items that are simpler to utilize and have remarkable recreation buildings are now readily available.
Dual treatment emulsions are the latest offered emulsions. Dual remedy emulsions will certainly have the biggest direct exposure latitude and are offered in numerous levels of water and solvent resistant functions. Dual remedy emulsions are midrange in cost, and greater solids content variations are readily available with affordable viscosity.
Capillary movies are a photosensitive emulsion layered onto a movie support. The name is a measure of the action that triggers the adhesion, capillary action. With damp screen material the movie will certainly draw into the mesh when positioned in contact with the face of the screen.
The step covering treatment can be made use of while getting rid of a few of the steps, or change the face finishings with all damp on damp finish strokes.
Capillary movies are very well used with the misting approach. Location the movie (emulsion up) on a difficult flat surface area.
In a filtered drying space or cabinet, will certainly dry screens in record time, typically less than half an hour. A dehumidifier will certainly drop emulsion drying time even more.
The step finishing treatment is made use of to coat a screen to discover your finest finish strategy for that mesh count. Coat once again the squeegee side on just 2 thirds of the screen, then coat once again one third of the squeegee side (all damp on damp).
Diazo emulsions are the least costly and the very first of the 3 emulsion types readily available on the marketplace. Diazo emulsions are mid variety in offered direct exposure latitude and can have excellent edge meaning. Disadvantages are that lots of need hardeners for long terms or water resistance lower solids material is frequently required for affordable viscosity.
When the screen is dry use the last coat of emulsion on the face side covering just one third of the exact same instructions as the last face coat, then dry. Choose a direct exposure time that fits the typical layer strategy and expose the screen with a test favorable that covers all of the layer modifications.
Stay constant and you will certainly have the ability to forecast your outcomes with higher precision. Your objective ought to be consistency, predictability, and repeatability.
With an emulsion stencil, more is not much better. Excessive emulsion on the face of the screen can trigger tough ink transfer and information can break down in a run. Emulsion drip from the mesh while drying is a guaranteed indicator that the layered emulsion is too thick.
Pure photopolymer emulsions are the most pricey and are very well matched with high quality single point direct exposure systems. Pure photopolymer emulsions have the greatest solids content offered with sensible and commonly exceptional viscosity.
Your emulsion maker can advise a finish treatment for each mesh count utilizing a rounded or sharp finish edge.
When the screen is dry, direct emulsion will certainly dry and comply with the profile of the mesh material triggering little hillsides and dips in the surface area. The smoothness of the dry emulsion can be determined and is represented by the term Rz value. The lower the Rz measurement number the smoother the surface area.
The solids material in an emulsion does not constantly show in the viscosity An example would be that pure photopolymer emulsions are offered in extremely high solids material with low viscosity. Emulsion viscosity can likewise alter with temperature level.
Location a screen (squeegee side up) onto the movie, gently mist the mesh with a spray weapon till the screen begins to prepare the capillary movie into the material.
Direct/indirect movie items are two-part movie and emulsion mixes. Direct/indirect movie systems incorporate the finest functions of direct emulsion and movie items, producing a strong, high meaning stencil that will certainly make longer runs possible with direct emulsion.