now the questions:
do i need to have a layer of silicon poured on my acryl too?
the projecktion surface is laying directly on the acryl isnt it?
how do i attach it? because i want to use a vertical screen.

i was thinking to make the frame hold the ir lights and the tracing paper and the acryl.

but wouldn’t the frame activate the reflection by pressing the siliconpaper to the acryl?
by that i mean at least at the sides.

how about using a frame over the first one that is not touching the compilant surface so the light from the first one is hidden?

thanks in advance.

In the interest of making this even easier, I’ve improved on the technique to apply the silicone.

I now thin it with Zylol at a 1:1 ratio, mix well, and pour it onto the vellum. Here’s the cool part that makes it easy-peasy.
I roll it out over the surface with a foam rubber paint roller like the ones they have at hardware stores.
The texture produced is micro-bumps on the surface. I applied two coats, and now the silicone layer is about half the thickness of the squeegie/fabric technique!

It produces blobs with a light touch, but it still needs a few more coats to be as sensative as the squeegie style sheet.  With this technique of application, it’s even easier to get a good, even coat of silicone onto the vellum so building it up in several layers is not so hard to do. It just takes a little wait time between coats. I waited an hour on the first one. It felt like it was cured up pretty well after 30 minutes, but I gave it another 30 minutes to be sure it wouldn’t lift.

I think I’ll make more and do about 5 or 6 coats.

Here’s a how-to video I made:

[youtube]http://www.youtube.com/watch?v=vvO_lvyDGVo[/youtube]

You can clean the roller pretty easily with the zylol and a rag. Just get the roller wetted out with the zylol, then roll out the excess onto the rag. Dispose of the rag in a fireproof container or hang it to dry. NEVER put solvent soaked rags in the trash. They can self ignite.

Have fun rollin the silicone!

Thanks in advance,

Gonzalo.

I’m new around here, and I was hoping to be part of this fine community. I decided to make my own multi-touch project; I’d like to start by making a LCD FTIR setup.

I wanted to ask about the compliant surfaces for FTIR setups. As I looked around the forum, different Silicon applying technics are mentioned. Could someone list and give a short explanation of these “techniques”? Also, what would be the proper layering for my specific setup. Being a LCD FTIR, I need a perfectly transparent FTIR compliant surface.

As of now, I’m thinking

no diffuser needed here
---------------------------- 120gr sketch paper (See this thread)
................................... 1mm thick silicone rubber - shor 40
================ acrylic surface

I’m hoping those layers will not distort the image what’s so ever.

Thanks for the help, very much appreciated.

And it’s Cheap!!!

It’s called Non-Woven Interfacing 305L1200 White (I think the code is store specific.) And it comes on a roll. I paid AUD$1.50 per meter!!!

(See pic below)

This material can be found at most Fabric stores (In Australia I bought it from Spotlight)
It is sort of see through and has a silicone like layer applied to one side of the material. (This layer is very thin and shiny)

I will post more pics of this material showing both sides soon.

The combination of (from bottom to top) Acrylic/Non-Woven/Non-Woven/Rosco/Laminating Sheet gives very good “Zero Force” results. The table still needs to be calibrated properly and I need to buy a projector for rear projection so it’s a little fiddly to calibrate.  Using a test projector the image from the projector difuses very well with the combination of the above layers.

I will add a YouTube Video soon of the test results.

Below is a screenshot from Touchlib showing the “Zero Force” applied to produce an image using my fingers [pic1] . in [pic2], I have placed a roll of tape on top of the surface and you can clearly see some FTIR effect being produced with “Zero Force” when the tape is rolled from one corner to the other.

Has anyone else tried this stuff out???

please tell me