@jegor-m thanks!
I’ve added photos showing the mirror-like effect.
The surface of #3 (baking paper) is matt and feels a bit rough.
#4 and #5 on the other hand are really shiny, flat and feel a bit like acrylic glass (although not really soooo flat)
Good prototypes. How is the surface finish of Prototypes 4 & 5 compared to the previous ones made with paper?
Prototype #5 was made like #4, except:
– I didn’t use a sieve when shredding, I just shredded the plastic multiple times and took out too big pieces in the end.
– I used 2mm spacing inbetween.
The results look very promising to me, I just have to add more material next time to get the sheets superflat and somehow make them even flatter if possible.
Hey! I recently bought 2 stainless steel plates (330 x 330 x 0,8 mm) and since I had ~ 200g of shredded plastic laying around, I decided to do some further prototyping with my sheets. For Prototype #4 I used PP shredded with sieve (6mm) and made a 1mm thick sheet. I heated it for 10 minutes on each side at 190°C and cooled it off afterwards in cold water. The result I got was by far the best I had since then. The surface is flat and shiny due to the steel plate.
PS: Sorry for the bad image quality, I’m taking the pictures with my 8MP smartphone camera which doesn’t really know how to focus^^ 
I’m wondering, did you use any plastic bags to make this sheet of plastic?
@jegor-m
Thanks for the really helpful tips & tricks!!! Thanks to that I was able to produce another, nearly flat, ~22cm x ~22cm sheet, about 2mm thick. I used the washers for spacing, that way the sheet got evenly thick, the pen is for size comparison. I will however build a of mould for fututre sheets, that way I also avoid damaging lots of baking paper due to molten plastic.
Thanks @carlf ! Sure! Have a look! I bought it on ebay for ~170€ incl. shipping, you can vary the temperature from 0-399°C and set a timer from 0-999 seconds. the upper part is heated and 38cm x 38cm (15″ x 15″) big. (so thats the limit of the sheet size)
@flo-2 ,
All the plates that were taken out of the mould straight away got warped outward. This is caused by the outer area solidifying faster than the middle bit. The outer bit cools down, contracts and forces the mid out.
To make a flat plate, you would need to cool it while it is in the mould, or at least fixed between plates.
I don’t know how your press looks like, but I guess you can take the plate out of the press and still have it clamped till it cools down.
do you have pictures of the machine flo?
looks really great!
@jegor-m thanks! And thanks for the useful information! Now I know what to test next 
What did you do to cool it? I took it out of the press immediately, carefully removed the baking paper and let it cool through the air while still on the wood used for compression.