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Anyone hear of a Epoxy & Aluminum Foil Emblem Copy Technique?


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#21 sjordan2

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Posted 07 December 2012 - 07:28 AM

Bill - can you add a little detail to the effect of using epoxy as a reinforcement for thin parts? How thick should it be laid on? Would it be a good reinforcement for fragile parts like wheel spindles?



#22 Pete J.

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Posted 07 December 2012 - 07:35 AM

I haven't done it, tho I very much want to. Here is my understanding of the process (someone with more experience please correct me where necessary):

1. BMF the emblem, do not trim it, rather leave like a 1/2" area around it. 2. Make a dam out of modeling clay around the emblem area. 3. Pour epoxy inside the dam and cover the emblem with some extra thickness. 4. After the epoxy has cured, remove it with the BMF from the car. This is the mold. 6. Pour epoxy in the mold and allow to cure. 7. Sand the back of the emblem until you just sand thru the BMF that is not in the cavity of the mold. 8.Take the finished emblem out of the mold, already covered with the remaining BMF. I hope someone who has actually done this will chime in. don't worry about hurting my feelings if i am totally wrong.

I've used this method with good sucess.  However there is one step that I changed.  Instead of pouring epoxy in the dam in step three, use white glue. The advantage is this:  When you have reached step 8 all you need to do is throw it in some hot water and let the white glue desolve.  This solves any problems with braking the part to get it free. 



#23 Art Anderson

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Posted 08 December 2012 - 09:46 AM

I have no shame. Here's what Art said about foil casting the other forum, where he's known as Biscuitbuilder (2nd post on this page). It's pretty much what Chief Joseph describes.
 
http://cs.scaleautom...ort=ASC&pi209=1


 
I have also seen recommendations to use Testors clear glass cement as a filler in the foil.

What I wrote on that forum was a description of the way Juha Airio made foil-cast scripts.  It might be wise to point out however, that with many model car bodies, the scripts have been engraved into the tooling pretty much to scale as regards the "height" of the detail (thickness of the script above the body surfaces) which can make any casting of such details a very delicate matter indeed.

 

In thinking about this factor, I reached back into my "memory bank" to an earlier time:  Back in the 70's, I was very deep into replicating Indy cars, and found myself in need of instrument details for race car cockpits.  Not wanting to tear up a possibly difficult-to-replace dashboard or instrument panel, I hit on the idea of making my own epoxy resin castings of instruments thus:

 

I used, for making small molds of instruments, "Silicone II clear sealer" which back then was a GE product, but is now produced by DAP, and is available in just about every hardware/home improvement section of the big box stores, not to mention Home Depot, Lowe's etc.  This is the old fashioned air cure silicone rubber sealer used to seal up shower stalls against the rim of a bathtub, and is thick enough to not require any sort of "damming" around the detail you may wish to copy.

 

To start with, you will need something to act as a :"mold release", as DAP Silicone II does stick readily to styrene.  This can be Vaseline petroleum jelly, but it takes only a little bit, wiped on, and then wiped down thoroughly to rid the surface (and the cavities in whatever script or detail you want to copy) so that the Vaseline doesn't have a buildup which would obscure a lot of that detail.  Next, squeeze a small drop of the stuff onto the detail, and use a toothpick to ensure that no airbubbles are trapped against the script or emblem.  Next, squeeze out a large blob of the stuff on top of that, gently spread it out a bit, but try for say, a 1/8 thick layer over the area where that script or raised detail is, and then let it dry thoroughly--generally about 24 hours.  Once cured, you simply peel the cured Silicone II blob off that surface, and you have a mold!

 

Now, I always smoothed the back side of such molds by shaving any peaks off of the cured silicone rubber, the idea being to get it to lay reasonably flat on the workbench.  Next I mixed up some DevCon 5-minute epoxy, spread that onto the mold, and again used a toothpick to make certain that all the details in that mold are filled, and not worrying about how thick the layer of epoxy might be.

 

After the epoxy has cured, it will still be a bit rubbery (flexible), so I simply would put the castings on an old cookie sheet, and bake them in a tabletop oven, but nowadays, a food dehydrator will do the same thing, at a lower temperature, but of course it will take a bit longer.  This hardens the epoxy considerably.

 

Finally, to thin down such details, I simply used a sheet of 400-grit Wet or Dry sandpaper, laid grit side up on a flat surface (used to use the kitchen countertop, but now use a sample of thick plate glass), with a small puddle of water between the back of the sandpaper and the flat surface, which keeps the sandpaper flat, and prevents it from moving around easily.  Next, I put a few drops of water on the grit, and placing the casting detail side up, simply scrubbed it gently in circles on the sandpaper, until I had sanded away the excess material to just the thickness of thin flash as one might see on model kit parts.  That flash could then be trimmed away with a brand-new #11 Xacto blade, and the detail will be ready to attach to the model.

 

Yeah, it is possible to break the epoxy details made this way, but if you break one, just make another one.

 

Art



#24 Ace-Garageguy

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Posted 08 December 2012 - 12:19 PM

Art, I've heard of this technique, possibly from you long ago. I've only seen one photo of a completed script though. Do you, or does anyone else, have any shots of a finished procuct? It sounds like a fine way to do it, but boy oh boy, so delicate. What do you use to color the final script, and what do you use to attach it to the model so no adhesive shows around the edges?



#25 426hemiman

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Posted 08 December 2012 - 12:42 PM

the only thing I do different is i use a dental gum massager instead of an eraser.



#26 Art Anderson

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Posted 08 December 2012 - 11:58 PM

Art, I've heard of this technique, possibly from you long ago. I've only seen one photo of a completed script though. Do you, or does anyone else, have any shots of a finished procuct? It sounds like a fine way to do it, but boy oh boy, so delicate. What do you use to color the final script, and what do you use to attach it to the model so no adhesive shows around the edges?

 I used the technique for creating resin casting masters, most notably on a couple of dashboards, the primary example being the AAM '62 Studebaker GT Hawk.  But the technique can be used for scripts, badges, door handles.  The caveat is, of course, the ability of a modeler to do all the really delicate work involved, and it can be very delicate indeed!

 

As for "coloring" the script, that's what BMF was created for--again, more delicate work!

 

Art


Edited by Art Anderson, 09 December 2012 - 12:01 AM.


#27 carrucha

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Posted 14 December 2012 - 06:27 PM

Very helpful tips.  Thanks guys!