So somebody gave me chocolate as present – in a fancy square transparent polystyrene container. What to do, except to eat them as quick as possible so that I can play with the packaging… (~300g )
Heated & shaped a small amount in a metal cookie container and realised immediately that it is much more tricky than HDPE/impossible to get rid of bubbles. Reheated and repeated several times, without much improvement. I don’t mind the bubbles inside so much, but the bubbles at the bottom in contact with the metal as well as the uneven surface is not desired.
Spend a day thinking on how to work with a larger amount into a bigger container – in my case a smallish tomato puree food can. Decided I’m overthinking it and would be better off by learning empirically while doing.
So I crushed the container, thrown everything in a large Teflon coated bread baking pan and proceeded to heat it. Once workable by hand (not ‘sticky’ yet) I pressed it by hand into the can. (by hand = in gloves)
For some reason I got lucky – limited bubbles that touch the surface:
The lesson here was that I got impatient and upped the oven temperature to 250 degrees Celsius. The black bits is either burn surface or the Teflon in the bread pan that came loose.
I also considered what finish options I should take – some sections are very smooth/shiny/clear, but others is not even.
Decided to experiment with my small sample bit first:
Machined it level in my Dremel work-stand and a 115 bit. I used a vertical bit position, which is not what the bit was made for really.
Lesson: polystyrene don’t like the machining – it is very sensitive to start melting and the melted ‘fluff’ block/rattle the bit. I gave up and not even attempted to mill to a depth where all the unevenness would be removed.
Proceeded to sand down the piece. The highest sanding paper number I had available was ~400. Not nearly fine enough. I gave up and not even attempted to sand out all the unevenness – I just wanted some areas as examples.
Decided to polish it more with my Dremel. That worked actually fine.
The dirt from sanding/polish compound I removed with a high pressure water gun – that worked really well, except that i got some water penetration as well (only a problem on transparent material and at a certain light angle) – I admit I tried to kill it with water though. More finesse & lower pressure might give better results.
I left the side surface of the piece unchanged – the cookie container have the sand-blasted surface. It would give you and idea what I had sanded out at the bottom.
Wow, really liked this Post. The pictures with the light coming up through the items looked very cool. So buffing and super fine buffing compound seems to be the go.
Super nice topic, relly informative! It didnt seem like you had any problems with white spots on your plastic after using toothpaste as some others have experienced… Did you wash the spots after, or did you have no problem at all with the paste?
– best from Denmark
Great work! Love your experiments. The products looks interesting and seems to have tons of potential. I would love to help out one day since i live nearby.
Once the two side was level, I got a better range of sanding paper: 180, 320, 600, 800 & 2000 (I really need something like ~1500 though)
The surface was still a bit smokey though, and understandingly I was very hesitant to go back to the Dremel polishing option.
Decided to give the toothpaste a go, and what a surprise! Absolute gold! Pictures below… It is clear that I need something between 800 & 2000, but other than that – I’m very satisfied.
Repairs: Not much to say, except:
a) to repeat that polystyrene don’t really liked to be machined in this manner. (Maybe a proper milling machine & bits will do better)
b) The micro pieces produced is ugly/unwanted
c) The silver lining of the disaster is an opportunity to level the side that had a dent in the middle due to shrinking as well as the border edge on the other side
Lesson here was that I could keep the Dremel position constant, but stepped the piece closer by adding paper advertising material incrementally underneath my working surface.
Decide to polish the orange piece a bit with my Dremel. Initially all went well, until I fitted a different bigger polish brush. I did not noticed that the smaller brush is actually a lot softer/more spongy. The result – the rotation of the harder brush melted grooves on top (a lot) and a small bit on the side where at that point I only noticed it:
Observations:
a) By letting the material flow by itself, I got a massive reduction in bubbles.
b) The bottom clear and orange did not bleed/mix a lot.
c) The top clear and orange did mix a lot, but the clear flowed downward first into the orange, squeezing the orange outward (it is darker there)
d) My wife really need to install a water level for her oven
At this stage I got sidetracked – I discovered old colored ‘slim’ jewel CD cases. I melted two orange ones. (Each was one half orange and one half clear.)
Method:
a) Only used 200-230 degree Celsius
b) Smooth cookie container for the final shape.
c) Kept clear and orange sections apart.
d) Added one third of the clear at the bottom.
e) Once that was melted and flat, I added the orange (that was melted & flat in a different container) on top of that. The orange was not 100% sticky yet and almost the perfect diameter. It only had to settle down without to much flow required.
f) Once the orange was melted & flat, I added the last two thirds of the clear (that was melted in a different container) on top of that. Everything was extremely sticky and soft at this point – resulting it was more a case of placing a round blob center on top of the orange and wait for it to settle.
I was very surprised how level and smooth it settled. But it took patience and sticking to the temperature range… with this result:
