With my second tests on the laser cutter I already knew that I wanted to use clear acrylic, but for this set of tests I chose to use 5mm not 3mm acrylic. I thought that this could be of benefit, by being sturdier and less likely to warp. Whilst it is sturdier the laser cuts to the same depth, so details of the picture are lost due to distortion. The thicker acrylic also slightly distorted when cuts, so as both would need to be flattened purely by pressure after there is no advantage, actually some disadvantages form the thicker acrylic.
With the three tests I did I left one with no cover, one with the original plastic backing and the final with masking tape before cutting. As before with no backing the acrylic burnt, less so then before as it was a smaller image, but it assured me that I will need some form. With the original plastic left on it made no marks and the image came out perfectly clear. There are some slight burn marks on the masking tape test, but these were caused when tested with no cover. With the masking tape it did not cause the acrylic to burn with the white marks, but instead the masking tape slightly burnt, giving a very effective slight greying to the image. This is very effective and makes the image stand out more clearly, whilst still being see through.
I tested with 3 different effects- halftone circles at 20 per cm and 30 per cm as well as halftone lines at 30 per cm. It was evidently clear that the halftone lines were much more effective for this process than the circles, so I need to test further what spacing to have the lines at in future tests. I was surprised by how poor the halftone circles where, as when I had been searching this was how the majority of lasers onto clear had been done, though I think not being able to change the laser setting may be part of the reason.
The process does not lead to the most easily readable image, and by having a less busy image it is far more recognisable and easier to understand what is going on. The amount going on in the first test was far too much, and I need to limit it to one or two people and maybe an object that they are interacting with. I also think that this could be a more effective way, showing the ghosts of the past only, and if correctly aligned it would be interesting.
For my last test, the one with the lines, I set the laser to 0.1mm rather than the 0.2. This does make the process take a very long time, as it doubles it and it was already a long time. Having the laser set to 0.1 though makes an incredible difference to the final image and is worth how much longer it takes, the detail difference is insane.
From these experiments I now know to stick with a less busy image, use halftone lines, 3mm acrylic and have the laser set to 0.1mm.