I got some clear colored removable silicone caulk at Menards in the US today.  They also had toluene, and the caulk was also toluene based.  I have to get some other things from the lab.  But I will try your method out tonight or tomorrow and report back with my results.  I’ll make sure to take pictures.

Has anyone tried pouring the thinned silicone caulk.  I didnt want to drop $50 on a spray gun.  I think I will try to pour the thinned silicone like others have poured the SORA CLEAR before.  I might have to experiment with the ratio of caulk/thinner. 

The stuff was really cheap.  $3 for the caulk and $10 for huge canister of toluene.

So I did try your technique.  I am currently waiting for the silicone to cure.  I will wait at least 24 hours.  Although its already very stiff (3-4 hours).
I took some pictures of the materials i used and the result.

I put the caulk (2 full tubes) into a paint can and then added some toloune and started mixing.  It was very think to begin with, so I kept adding little amounts of toloune until it had a slimy consistency that was easy to pour.  I poured it through a paint filter hoping to get some air bubbles out.  It helped a bit.  I found the higher I held the paint filter (ie longer pour distance, the less bubbles i got).  I had a lot of small bubbles in the beginning that all went away though.

After I poured the whole mix (i had about 1/3 of my paint can), i used a plastic spoon to spread out the silicone everywhere.  I was hoping to use a ruler sliding a long the wood pieces i put down.  I tried, but the way i taped the wood down was bad, also my ruler was too flexible.  I should have thought better about the setup for this, but i was too lazy to go back to the hardware store.  In the end the ruler made things worse i think.  I ended up using the spoon to finish things off. The silicone was fluid enough to smooth itself if left alone for about 30 sec.  You cant see much difference in the pictures below.  The silicone layer is very clear.  I do have a few bubbles and uneven spots.  Also I think the floor was not very even and one side of the silicone layer is thicker than the opposite ( with a gradual increase. 

Im excited to try it out with the projector tomorrow.  I ended up doing a messy job, but the silicone is very clear.  I think the projecting through this onto my mylar will work well.  I hope the somewhat uneven surface and other mess ups will still render the sheet as a good compliant surface.

before (left) and after(right)...you cant see the silicone n this picture (sorry bad lighting) it is very clear.  The fluid like thing on the right is because some of the silicone got underneath the acrylic.

How to remove bubbles cheap and easy: Quicktime or Windows Media

At the very end of the video it describes the “bombs away” method which works very well (in my experience).

**Make sure your acrylic is perfectly level when applying**

It works!!!

It works pretty good actually.  I have to fiddel with the projector and camera placement for a while. I think I’ll also need a bigger mirror. I’ll take a video once its setup.  The silicone is very clear and hard.  With Mylar on top I am getting rather bright blobs for zero force touches (not as bright as directly on the acrylic, but sliding fingers is much better). 

The mylar tends to stick to the silicone from time to time.  This doesn’t cause any FTIR, but you can see it on the surface and the projected image.  Does anyone know of a way avoid this (I tried two sheets of mylar but that didn’t help)?

I have heard baby powder (talcum) or trace paper works.  I am excited. I plan on trying the cheap caulk tomorrow.

trace paper as a rear proj. screen… works

look ar my video, there is only a paper on the box:

http://www.youtube.com/watch?v=TGs-fW8vkP4

Hi,
I’m really glad that someone else got great results out of my technique. Thanx for posting your results. I dont use mylar or tracing paper so i cant give you advice on this. I can tell you that the rosco keep ‘’sticking’’ like you explain for a week. Maybe curing time is longer than 24 hours. I didnt use any powder and the problem is gone after a week. I think your product look similar to mine an i hope you enjoy touch free effect as i do. I will receive my new computer this week so it will give my mt a bigger heart.

thanx to everyone
Christopher

I took it one step further and used toluene-based Lexel thinned with more toluene. The more toluene you add, the easier the bubbles disappear, but the more fluid and messy it is. WEAR GLOVES! I can’t stress that enough. On a perfectly flat, level surface, you should be able to create a shallow pool with tape and metal runners so that the surface will be an even liquid-level at whatever thickness you desire.  I used two cans and two paint filters to eliminate bubbles, combined with the bombs-away method of pouring eliminated 99% of bubbles. Later on I could pierce a bubble with a needle and fill in with Lexel from a syringe and it would disappear, bonding seamlessly at the molecular level.  Other surface defects can be fixed in a similar fashion.

The PDF says it’s stronger and more flexible than silicone and 19 TIMES CLEARER!!! So… we will see when it’s cured.  I will upload pictures when I can enter my room again without getting REALLY REALLY high on the fumes. If the blob detection is increased and it isn’t tacky like silicone, then I will start another thread with pictures and instructions.

I did spill a little bit on one corner. I’ll fix that later.  I may do the whole thing over again. Otherwise, it all looks okay.

Okay, I’m starting a new thread, this stuff is totally awesome! I screwed up a corner, but it’s soooooo easy to fix with a little splash of toluene. It dries very slightly misty and a little bit rippled, so splashing a final wash of toluene (outside) eliminated the ripples and made the Lexel layer _completely_ clear. I mean glass-clear.  Sparkling. This stuff really is 19x clearer than 100% silicone caulk.  So easy to work with.  If you screw up splash the whole thing down with a lot of toluene and try again.  You can fill bubbles with a drop of toluene for tiny bubbles, or toluene-thinned Lexel for larger bubbles to avoid surface depressions. I want to get it absolutely perfect with a bunch of photos and test videos.  It turns out the thinnest non-woven Pellon I had works great to eliminate the stickiness of the Lexel, but I’m still looking for another method like silicone oil.  My Rosco arrives tomorrow, so I should have a tutorial finished by this time next week.

I think Lexel is the absolute cheapest and best compliant surface material.

I totally agree. here is a video of my first hardware test with this as a compliant surface.  I thought I might try sorta clear also.  but if it gets better over time as christopher suggested, this might just be fine.  I can confirm Adams observations that blemishes can be fixed with some extra toloune solvent.  I also tried this as I thought it might disolve uneventies just on the top of the layer...and it works great!

I think I might do it over again, having done a messy job the first time around, I would love to help with a tutorial, we should put it on the wiki.

That all sounds really cool, I just wonder how this solution compares to Sorta Clear 40 in terms of performance (table sensitivity).
Has anyone tried both approaches?

Hi everyone!

Adam: I’m glad you’ve got great result! Transparancy of my product its not a problem, so you should not care so much about the 70 time more clearer.... Image is perfect!!! I’ll post a new video with better image quality....I always said it was possible to pour it but I’ve never tried so im glad you and Thomas Hansen made it…

GFantini: I think its gonna be really hard to compare as long no one seem to use the same product. I’d like to test sortaclear but its really costly for, i think, really similar result. I’m really confortable with my setup its really zero touch compare to bare acrilic.

I was suppose to finish the esthetic side of my screen but my work and my new girlfriend took me a lot of time so this week end I’ll make another video of my unfinish screen...(was suppose to make it after its done but....)

I have tested the Sorta-Clear 40 and 100% silicone caulk on separate scrap acrylic.  I didn’t have a working documentary camera at the time and have since donated the samples to a fellow MT researcher for testing, otherwise I would have shown a video of the difference. The difference I found was Lexel had the lowest refractive change from acrylic to projection surface. This was evident in the lower “glow” of the screen when illuminated with IR.  Right now I can track fiducial markers and pressure because of how little refraction/reflection of IR light. This has led me to investigate all the different ways of attaching the IR LEDs.  I have found that a slight angling (30°) away from the compliant surface removes the glow, hot spots, and any ghosting from finger-drag operations. Jeff Han mentions 30° as being ideal for FTIR. Also, baffles are important for eliminating edge-glow which slightly increases as the angle increases.

Sorta-Clear 40 and the caulk were too difficult to apply evenly at the right thickness without defects, expensive, and let me say they _SMELL_ really, really bad.  The performance differences were nominal.

I have read somewere that lexel was clear enuf to track fiducial, if its true this stock look really clear. Definitively better than mine but i just wonder about the hardness of it. It seem to be ordinary silicone and those are really softer than mine so id like to know about it. I’ll try to fine some by here..

thanx
Christopher