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One thing to remember about clear epoxy resin is that it will eventually turn yellow.  Clear urethane resin doesn't.  

Just out of curiosity ,, How long until it starts to yellow? 

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That sounds like it might work out well, Steve. Getting the exact amount of material measured out so that when it does melt and conform to the shape of the mold, there is little to no trimming nor sanding of the backside would be ideal.

Are the backsides of your lenses smooth, or asked a different way, are the front faces of each lens textured?

Yes, the lenses that I have experimented with have the texture on the face.

I really haven't been able to figure out a scenario in my brain where something like this could work with the texture on the back side.

 

Steve

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 In my search for good kit-sourced lenses, there were very few which looked like accurate representations of the real 1:1 sealed beam lenses, but the Revell '69 Camaro kit was one which stood out as containing nicely detailed lenses.

I always thought the Monogram 1970 Buick GSX kit had very well done headlights, complete with the T3 triangle in the center.  Of course, being a 1/24 kit, they might not be adaptable for most 1/25 kits.  Plus technically I believe they're only appropriate for GM vehicles through 1972.

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I wonder if one could make a mold with aluminum foil off an existing lense.  Sit in baked clay as an example.

Lay a predetermined slice of cut off clear sprue in said mold . then put it in an oven  to basically melt and form itself to the foil.

 

I guess it would only work if you could remove the foil once cooled

 

just thinking out loud

 

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Just out of curiosity ,, How long until it starts to yellow? 

In my experience, it depends on the thickness/mass of the part. A thin piece like a lense might take a while, but a thicker piece, like a casting block for the lenses, will start to show yellowing within a month. Exposure to UV will accelerate the process. 

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I wonder if one could make a mold with aluminum foil off an existing lense.  Sit in baked clay as an example.

Lay a predetermined slice of cut off clear sprue in said mold . then put it in an oven  to basically melt and form itself to the foil.

 

I guess it would only work if you could remove the foil once cooled

 

just thinking out loud

 

That's basically what I'm doing.

Only I'm using mold putty instead of foil or clay.

The high temp seemed to have no affect on the cured putty in my first trial.

The lenses pop right out of the putty mold.

 

Steve

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In my experience, it depends on the thickness/mass of the part. A thin piece like a lense might take a while, but a thicker piece, like a casting block for the lenses, will start to show yellowing within a month. Exposure to UV will accelerate the process. 

I was just wondering because the ones in that pic were done almost 2 years ago and don't show any yellowing at all yet.

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My second experiment with the sprue melting theory didn't go as well as expected, but it did reveal an interesting phenomenon.

I first tried just cutting a piece of sprue with a sprue cutter & laying the pieces in the mold.

Even at 500 degrees I couldn't get it to flow into the mold, it would be difficult to determine the exact amount of plastic to use & I wound up with a lot of air bubbles.

So then, I first heated a piece of sprue to the melting point, pressed it into the mold to get a uniform shape & size & then cut it & set it in the mold for reheating in the oven.

The problem seems to be that the plastic never really "flows" into the mold.

It beads up much like a drop of water.

But, this gave me an idea!

If I made a reversed mold, in other words using a lens with the ridge detail on the back side, the plastic will melt enough to give you the ridge detail & when it beads up, it hardens with a perfect shiny smooth surface.

Now, if I can solve the plastic amount issue & resolve the bubble problem, I may have something that works!

I'll get back to you.

 

Steve

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  • 2 months later...

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