Experimenting in the lab
We spent a little time recently experimenting with a new technique we’ve been dying to try out - high density printing! This is not a new idea, it’s been around for ages - but you don’t see it very often.
This specialty printing technique is another example of how screen printing can offer things for your branded merch that the age of digital printing can’t. Direct-To-Film (DTF) and Direct-To-Garment (DTG) can’t do this.
The process starts like any other printed design; with your screen preparation. For our High Density (HD) print, we started with a 160 mesh screen, two coats of emulsion on the print side, followed by 6 coats on the ink side. We let that dry in our cabinet and came back for it later to check the emulsion thickness over the mesh (EOM).
Our readings told us our screen had a thickness of 290 microns; we thought that was good enough and moved on to the next step: exposing the artwork.
One of our typical screens exposes in 15 seconds on our exposure unit. With some EOM readings and simple calculations we determined that we’d need to expose the newly coated HD screen for about 45 seconds - nailed it.
After the screen was exposed, we took it to the wash out booth; it took a bit of convincing but it cooperated eventually. Remember this screen has A LOT of emulsion on it, so it took longer to wash out!
Comparing the stencil on this screen to any of our other stencils was a great learning exercise to physically show our staff something we can normally only describe. You could SEE and feel how thick that stencil was. The stencil thickness is an important aspect of screen printing; it is one of the factors that determines how much ink your squeegee is going to print. Our stencil thickness is normally quite thin - and we like that; it makes our prints thin and comfortable to wear. A stencil that is around 120 - 150 microns is going to hold far less ink than a stencil of 290 microns - almost double the thickness actually!
So our screen was now ready for print - let’s begin!
It was immediately apparent that this screen was laying down a lot of ink! We put down one layer, hit it with the flash cure, followed by the roller to smooth that ink down.
After that, we laid down a couple more layers and watched the ink build up, flash curing the ink between each layer.
We got the final result that we were looking for on this experiment - a three-dimensional print with crisp edges; a print that looked like it was made out of PVC and somehow attached to the garment.
What did we learn with this experiment?
We learned how to do this, but also how to do it better next time. First thing we’d do differently next time is choose a lower mesh screen. Lower mesh screens hold more emulsion; so our EOM number would be even higher, meaning a thicker stencil - and that means a thicker print.
With a thicker print, we could build up our desired thickness in less time and fewer layers. With our initial experiment, it took us about 10 layers before the print really stood out on the garment, and we kept going until we hit 15 layers. It would be much more economical if we could do the same effect with 2-3 layers… in an ideal world! All of our crew got their own new hoody printed with the new HD technique and were asked to wear, wash, dry, fold, and pick at their new threads. So far these prints are bullet proof (not just because they’re so thick), and we’re looking forward to whipping out this technique for someone’s new merch soon!
