I was just wondering about the discussion on the silicon layer.
Both Elastosil and Sorta Clear for example, are both originally supposed to be used for building casts for sculpting etc..
I just wondered if those types of Silicon (don’t know much about cemistry) run through some changes overtime (the are for example etxtremly heat resistant. ok thats surely a feature of silicone itself),
that have an impact on their ability to work for such setups. Maybe there are still other types of silicon, whose primary field of application is isolating and covering or something.
@rogerj: do you have any info on “how” the silicon changed? Did the material itself became less transparent or something, or became more sticky, or both? How thick was your layer?
Just guessing, maybe this can motivate to have another discussion on silicon?
Tinkermans approach resulted in a REALLY thin layer that works amazingly good.
So in this approach maybe there is a chance to use very diffrent silicones (Tinkerman just used one from the hardware store), cause you don’t need to make a rather thick layer (comapred to tinkermans layer) that has a good factor of transparency. Was that not the primary decission to use sorta clear for example?
Sure, the material should have a stability that keeps the texture preserved over time.
Rogerj and I are working together. The video I posted demonstrated some of the change over time. As the plotter texture used to work nice and now doesn’t and the frosted polycarbonate texture had major trails, while now it doesn’t. The thing is, most silicones cure over time. They cure to touch and form within a day normally, but they don’t fully cure for sometimes weeks.
The frosted polycarbonate turns out to work the best out of all the textures tested so far. It leaves the silicone looking just like frosted glass and is great with projection, but we’re still interested in more method’s a easier solutions like this one.
just to get it right: do you use the polycarbonate sheet to get a texture on the silicone (like tinkerman uses fabric to give the silicone its’ texture )?
Or do you use the frosted sheet on top of a NON-textured silicone layer?
Maybe you already described that in a different thread, but could not find it
So the overall problem is, that, when using silicone, in most cases it looses its structure (especially the tiny air packets) over time and gets more and more connected to the acrylic, thus, the FTIR Effect gets worse?
RTV (Room Temperature Vulcanization) silicone curing commences when the product is exposed to atmospheric moisture, with elimination of by-products. This reaction, also referred to as vulcanization, begins at the surface of the applied layer of silicone rubber and gradually progresses inwards. Depending on the type of crosslinker used, the curing system can be one of three kinds:
Basic or amine systems: small amounts of an amine are eliminated.
Acidic or acetoxy systems: small amounts of acetic acid are eliminated. (what tinkerman uses) Neutral, i.e. oxime or alkoxy systems:small amounts of an oxime or alcohol are eliminated
Catalyzed silicone rubbers are composed of two components, designated A and B. In platinum-curing, polymer chains are linked through a hydrosilylation reaction at the vinyl groups by means of the hydrogen-containing curing agent.
RTV stays the same with time. Nice & squishy. Pourable silicone does not. It can and does degrade with time. I have a ten year old silicone mold I made from 2 part 3M stuff, and it is now not nearly as elastic and it can split easily.
As far as how long my silicone will produce blobs goes, time will tell. I think it will hold up very well.
BTW I measured my vellum/silicone sheet’s thickness with a caliper. It measures about .012” thick That’s about three human hairs!
Sorta clear is a two component based silicone rubber (as well as Elastosil). Might be a problem, then, no?
I am not sure, but if i get it right, those silicones might not be the first choice after all?
Exactly!
Maybe this thing I’m doing with off the shelf silicone will last longer, and it’s way cheaper, readily available and pretty easy.
Part of my design philosphy here is to utilize common materials that can be easily purchased at a hardware store.
This makes it easy for DIY people to get a table built and experiment, develop apps, etc.
I got some vellum sheets laminated today.
I had them do two at a time in the same pass, then I cut them around the perimeter and ended up with two sheets of vellum with nice clear protective laminate on one side.
I’ll texture some of these up tomorrow and see how it works.
The laminated vellum works great! A little less touch sensitive than vellum/silicon alone, but I have a protected surface.
I took a second piece I had laminated, silicone texxtured it and applied IR blocking window film to the top laminated surface.
It filters out a good portion of ambient daytime IR room light. Now to find some in clear, not tinted.
I have some new fabric I’m going to use for texturing and I’ll try it out today.
It has a slightly courser weave which should create bigger bumps in the silicone.
Thanks for all your work! I just got my preliminary frame built with 18 LEDs spaced 1” apart on opposite sides of a 18” x 24” piece of acrylic. My blobs really don’t show up that well so I’m looking for a really cheap way to get blobs like yours (college = poor.....) So when I saw your post with off-the-shelf silicone, I got really excited. I started looking around for drafting vellum and found a few different weights and types. Do you know what weight you have? Or better yet, can you tell us the brand and from where you purchased it? I appreciate all of you work on alternative compliant surfaces.
It’s made by Helix and I got a pad of 50 sheets at Office Max for about $38
$0.76 a sheet isn’t so bad… Don’t know what weight it is. Meduim maybe
It’s made of 100% cotton rag. It’s all those mircoscopic natural cellulose fibers that duffuse the light so nicely!
Thank you for the quick reply, Tinkerman. I have a shopping list for tomorrow. I’ll try to post pictures within the next week or so (I’m in the middle of moving...so probably early next week) to let everyone know how it went. This seems like a promising alternative to people inexperienced with pouring silicone. Thanks again!
I have the screen with the texture from the latest fabric on the table and it works great! Better than the first one.
This is one of the laminated pieces and it’s got a good feel.
I just got fine woven polyester fabric today and some transparent silicone from the hardware store (it’s labeled highly elastic and fast curing).
Hopefully i can reproduce tinkermans approach
When i get my rosco order (i ordered gray AND black), i am looking forward to do some experiments on layering the rosco with diffferent layers of plastics,
to get a protective layer that can also be replaced when scratched. I had a little talk with a rosco retailer, and as said in the catalog, the black one is designed for rear-projection
setups with lots of ambient light (i think i also read that on the forums?).
By the way: has anyone used differnt protective layers? I read some entries on the forums about protective film, but i am still looking for a good layer
(not to light to let the rosco wrinkle, and not to heavy to make it less sensitive to pressure). As i’ve choosen a flat setup table i think that will do, hopefully.
Well as soon as i can contribute some results, i’ll let you know!
My goal is to have a layering that works (from bottom to top):
-acryl
-thin and textured layer of silicon (like tinkermans’ (hopefully ) )
-rosco projection screen
-protective layer (still not know what to use)
I just tested the textured silicon I made on a sheet of tracing paper according to Tinkerman’s technique and I’m currently getting mixed results.
I intentionally made it so that the thickness would vary from one edge of the paper to the other. In the region where the silicone is thicker, I get incredibly bright blobs, but the silicone tends to stick on the acrylic, leaving permanent bright spots. In the middle, where the silicone thickness is rather thin, I get blobs similar to what I was getting with untextured Sorta Clear 40, which is good enough. Towards the opposite edge, as the rubber gets thinner, the blobs get more and more faint.
One thing that I noticed was that in the few regions where I got the texture nice and crisp, the blobs tend to be very nice with no trails. So I’m doing it all over again, and this time I’ll try it with two passes to see if I get a more pronounced texture.
The fabric I’m using is a coarse nylon mesh I got from the silk screen store. I also got a thinner, smoother one I might try later.
The beauty of this technique is that I can screw up many times without spending a fortune. So far, the results show potential. Good stuff, Tinkerman!
Like others in this group, I have a passion for this and I love fostering it’s development by sharing my hardware input.
That bright sticky blob stuff happened to my first test as well. Come to find out, it went away overnight, and has been making blobs that release nicely ever since.
RTV silicone reacts with the moisture in the air around it. That moisture allows the acetic acid in the stuff to evaporate. As it does, crosslinking takes place rather rapidly.
It cures from the outside in, and it off gasses for several hours. That’s why you get he initial sticky effect.
It should go away with a little time.
