Latex vs Silicone

[Nick Lewis]

On 2/16/2025 at 4:13 AM, fiddlecollector said:

I was putting a TPU screen protector on my phone yesterday ,has anyone used TPU film , seems to have some good properties if you can find right thickness?

I used TPU to make a packraft. Really cool because I could iron the seams together and no sewing required. Unfortunately all the material is quite thick so not good for testing this application. 

[christian bayon]

On 2/14/2025 at 3:25 PM, lFred said:

If I recall correctly @christian bayon at Schimitt lead paper/film was used.  I do recall it was a metallic film of sort but doubt it was aluminium, as from my souvenir it did  not wrinkled.

I think it was tin foil, before the use of more practical latex.

[LCF]

Here's an update on this topic with a few pics below. I was puzzled when the silicone arrived due to the packaging and the colour. There was a polyethylene layer and a mylar layer but it transpired that the silicone was bonded to the mylar and I had mistakenly ordered black rather than clear. It peeled off easily.

This is the 0.1mm membrane and it is quite stretchable, a little stronger (stiffer) than my home made latex film of the same thickness. It is also a bit sticky feeling although not self adhesive so I dusted it with talc.  I've ordered some clear but proceeded with my test anway using a worthless Markie top plate.

There is a pic of the membrane clamped in situ followed by the same under a mild vacuum of approx 2" H2O to get an idea. I did not use the vacuum during the cast.  My foam dam is 1.5" thick as per Brad's (and others) suggestion. I recall a photo of @Mark Norfleet 's wooden dam, much deeper, and now I understand perhaps why, to get more plaster pressure for finer detail at the edges. Otoh a higher vacuum would give a similar result. This simpler type of cast is nonethless perfect for my current projects.

 

 

[LCF]

Two further pics, both under that same vacuum which I chose because it has approx the same effect as 1.5" depth of plaster. 

Firstly the pallet shrink wrap 0.02mm l  looks about the same as the 0.1mm silicone. Second pic is my home made latex approx 0.08mm thick. It pulls down better at the edges General plate area no different to the other membranes though. You can see the brushmarks from when the latex solution was spread out on a sheet of glass.