Experimental Lens Casting -UPDATED !

[Skulldigger]

I am in the middle of an experiment and probably against my better judgement I am going to share with you guys. If it is a success I will be glad I did, if it's a flop I well, will just have a flop...lol.

I am in need of a glass lens that stands a low chance of actually being found. So I am trying to create one with a strong polyester resin. I am using a molding material called Amazing Remelt, which creates a gel mold for casting. So far it seems to be going well. I experimented on a few other objects before I started on this lens.

This is the lens I am trying to reproduce. It is a 1940' - 50's glass Cats Eye bullet lens. You can find these everywhere in 2-1/4" to 2-3/4" but this one is 4" in diameter at the base. Probably only made for the Sireno R5R siren/light combo.





You actually melt the molding material in the microwave. I made a form and filled the lens up with clay and placed it in the mold as you see it sitting in the picture above. Then I slowly poured the material over the lens and filled up the mold.Took about 3-1/2 pounds of material to cover it. After it dried over night I took the clay out of the lens and cleaned it up, then I cut a piece of plastic to act as a divider and laid it over the top. Then I poured more molding material to fill the inside of the lens and cover the top with about 1/2" of material. After it dried, again over night I removed the lens. The mold looked perfect !

The I mixed up the resin and poured it into the space in the mold and filled it up about 3/4 of the way. The slowly put the center in making sure the resin was distributing evenly, especially around the lip of the lens. It has been in there for 24 hours now and I just removed the form.

Here is the mold after removal from the form.


It has been in there 24 hours now and as the resin is hardening and you can actually see the lens developing inside. It's like taking a sonogram of a baby !

Here we can see the base of the lens, it is very round and the lip appears to have formed completely. There is visual distortion because of the material, but it looks to be correct.



And here is the other end, check out that detail ! I am lighting it form the other side.



The bubbles are in the mold not in the resin. Shining the light through it I see no bubbles at all in the resin!



I added some red dye to the resin as I was mixing it so I am hoping it comes out red. If not I will use some glass paint to color it from inside. Keep your fingers crossed for me ! This could open up some real possibilities not only for small lenses but for small parts as well.

 

[Stampeed Valkyrie]

Very cool

I hope it turns out well.

 

[StEaLtH2]

Necessity is the mother of invention... great work, I too hope it works for ya

 

[Scoot163]

So did you use an actual lens to make the mold? Or just create the mold to look like a lens. Michelangelo would be proud.

 

[Skulldigger]

So did you use an actual lens to make the mold? Or just create the mold to look like a lens. Michelangelo would be proud.

I have two Sireno R5R's one with a lens and one in need of. I used the one I have to make the mold. If one was artistic you probably could make one from clay.

 

[toon80]

If it turns out well, and it looks like it will, you will have a business, my friend

I know people who have been trying to make this happen with different materials, but your technique looks to be going well so far,

 

[894]

I'll be dipped, or molded, as the case may be!

What about 3D printing? There was an episode of some show a while back where a car-restoration shop sent out two crazed/cracked/faded rare taillight lenses and had them reproduced through a 3D printer facility... in the event you're not successful. I looked into that possibility a while back but only found two fledgling firms near me that weren't real sure about the accessibility of the material needed for printing the lens I was attempting to reproduce. It seems THAT is the only issue, in that new industry...

I have had luck with different epoxies and tinting with translucent paints in repairing obsolete lightbar domes in the past but nothing on this scale!

We await the results!

 

[bmd224]

A couple ideas:
1). Is that lens perhaps the size used on carnival rides like kids ride at a traveling carnival? The motorcycle ride with those annoying horn buzzers comes to mind.
2). Check with a mom & pop jeweler who does 'lost wax casting'. It's an ancient art used to make jewelry/rings that's still used today by most small time jewelers.
Good luck!

 

[Pete L.]

I only have one thing to say:

"You're only limited by your own imagination".

Looks good !

 

[Skulldigger]

What about 3D printing?

I would love to try 3D printing. I think it would work really well, although I wonder if it would be as smooth as this should turn out to be? Plus the cost. I have found a 3D printer for about 1K which isn't bad. This stuff is not cheap either, the remelt is $40 for 2.5 lbs and I am using about 5 lbs total.

2). Check with a mom & pop jeweler who does 'lost wax casting'.

Not sure the wax would work with resin, it warms up as it cures.. of course this remelt, melts at 120 degrees.. so wax may do the same. Will have to check into that. Wax would be easier to work with I think.

Most places I have looked recommend Silicon molds, but that stuff is real expensive, about $100 for half a gallon, and it's not reusable. Make 1 mold and you just have one mold. This remelt can be remelted and make a different mold.

 

[Skulldigger]

Well after some researching and careful thought I decided to remove the lens from the mold this morning. It is cured, although it will continue to harden for a few more days. I have to say, although it is not perfect and has a few undesirable flaws, this was a success. I think I know what caused the imperfections and will try it again.

Here is what is left of the mold, it had to be destroyed to disassemble.



It has a few problems. The center mold shifted to one side and so I have a bit of a twist in the lens. The coloring is a fraction of what I put into the resin. When it was poured it matched a Federal red lens perfectly. But this was a translucent dye, I probably need a solid dye.


Where the center shifted it touched the side and it gets thin on one side and in fact there is an opening where the resin did not form.




It doesn't look awful and will fill a void until I can try this again.



If I put in a red bulb it makes up for lack of color. I almost wonder if I should do the next one clear and use a red bulb.



At least now I know this is do-able.

 

[StEaLtH2]

excellent venture into uncharted territory.

 

[Tony P]

I'm impressed

 

[Scoot163]

Great work and great innovation! Inspiring!

 

[kadetklapp]

Don't give up. You could theoretically repro full domes using this method...

 

[dmathieu]

AWESOME!

 

[kerry4951]

Congrats!! I would call that a major success

 

[lotsofbars]

Nice job. I have an old Signal Stat dome that I need to be reproduced as it has two gigantic cracks and I've almost thought about doing something similar to this. It would take a LOT more patience and time than I'd be willing to spend on something like that though. Hopefully 3D printing will soon be able to make a reproduction of whatever we'd need.

 

[Skulldigger]

Thanks everyone.. I am encouraged.

Two problems about a full size dome. Although this Polyester Resin is clear it is not distortion free clear. It resembles ice more than glass. For something like a full size dome it would have to be in a silicon mold. This little lens really should be in a silicon mold. I went with the gel first because it is cheaper and reusable. This took $80 worth of molding gel, but I can remelt it and reuse it over and over again. In fact I have used it already to replicate a knob on one of my wife's antique canisters and a pull on an antique chest we have that we could not find a match for. They are identical !!

The silicon for this project would have been about $150. The advantage of silicon molds are once you get a good mold you can use it over and over to make multiple copies. But you can not make a different mold.

I am going to start over tonight. I'm going to make a new mold. I know where my mistakes were and hopefully I can eliminate them this time. It will be Thursday or Friday before I know. Slow process.

 

[lenny77]

very nice.. likes the thought process. now make it spit out an aurora B.

 

[Skulldigger]

I put on 2 coats of Testors Transparent Red. World of difference. If the solid dye doesn't work out this probably will on the next one.



After painting, if the cast was solid I could actually live with this.

 

[JazzDad]

You later mentioned silicone, and RTV will probably give you the best results for reusable moulds.

Dyes will be tricky. Something that has good colour today, may fade with the smallest exposure to UV.

Very good result so far!

 

[jph2]

Your ingenuity to come up with this is amazing. And your first result turned out very well! I have no doubt your next one will be excellent. I think it's really neat how you made your own lens.

 

[Maxim2Eng]

Outstanding effort with very encouraging results! My wife used to make jewelry and used the lost wax method on several pieces...they are all one offs as the mold is lost after casting.

Next time you make your mold, make sure you cast an "index key" so the inner and outer molds will line up properly. Use 1/2 of a pop cycle stick vertically next to the rim of the glass lens in step 1 and remove when cast. In step 2, use another stick with a notch cut out to lay over the outer mold and fit into the key in the outer mold. Pour it in the inner mold and leave the stick in the mold...it will line up perfectly. It may result in an imperfection on the rim of the new lens, but one you can file off. Also, PAM cooking spray on the lens helps it separate cleanly. My $0.02.

 

[Skulldigger]

OK.. The second try came out of the mold today. Not easy, but it is out. I should have used some sort of mold release. I used a lot more coloring to get the right red and came pretty close. I had everything centered and this lens came out really well. I am quite happy with it.

The new lens is installed on the chrome siren, the original lis on the copper. The first casting is sitting on the table.





Both lit up !


From the side the Cats Eye effect is pretty good !


From the end. The built in Fresnel actually works (L)

Left Polyresin casting, right original glass lens.

 

[dmathieu]

WOW!!!!

 

[Scoot163]

Pretty damn amazing! Impressive!

 

[kerry4951]

I am very impressed!! My hat is off to you. Looks to me like you nailed it.

 

[ex416]

that turned out great.

 

[jph2]

That is amazing work right there! That looks as close to original as you can get!

 

[Crownfire]

You're quite a talented guy. We're lucky to have you here on the forums and in the hobby.

 

[bmd224]

This looks amazing!
So, when will you start making domes for Mars Aurora Borealis, Fed Sig Beacon Rays, etc.?

 

[JazzDad]

Not so fast. He's working on one for me.

Here's Skulldigger contemplating the process for my lens.

 

[Skulldigger]

By cracky I think we can do it. But it seems extreme to just use for burning ants.

 

[Maxim2Eng]

Recently, I came across this company Smooth-On while doing research on making endcaps for Dietz and DualComm bars. Saw this video and remembered this thread.