OLD Johan acetone/acytate bodies

[Khils]

Have any of you had any success working with the unwarped portion of the old Johan promo bodies?  I myself have notice the painted portions...such as a two tone paint scheme are not severely warped as the unpainted parts.

Also an success grafting these to the current styrene?  2part epoxy or CA?  Or combination of both?

I respect your input, failures & victories....ALL appreciated information Please.

[Ace-Garageguy]

ACETONE is a solvent.

There's no such word as ACYTATE.

ACETATE is the plastic you refer to, and yes, epoxy will adhere to it just fine.

[Art Anderson]

CA or epoxy are pretty much the only glues that will join Acetate plastic to polystyrene.  Solvent-based cements will bond Acetate to Acetate, styrene to styrene, but the two plastics are way dissimilar, they don't dissolve and bond well to each other.

Art

[Khils]

Sorry Bill....gluing the finger together...NO problem....spelling.     Well another story.

But yes that is the direction I was going.

Thank you Art .......that is exactly what I was wanting to know.

[Ace-Garageguy]

....gluing the finger together...NO problem....spelling.     Well another story.

  Sounds like you my have a very interesting project in mind.

A decent epoxy will give you a stronger bond than CA, and like any glued joint, the strength of the bond is in direct proportion to the AREA of the bond.

All this means is that a simple edge glued to another edge won't be very strong, and will tend to fail at the joint if you do any serious heavy bodywork...which I assume you intend to do if you're attaching large acetate sections to styrene.

Any way you can spread the bond over a larger area, or reinforce it, will be very helpful.

I do a lot of heavy parts swapping.

And I ALWAYS reinforce the backside of the joins with very fine fiberglass cloth, made for RC aircraft, and more epoxy. This is important to prevent cracking on styrene-to-styrene joints, and will be doubly important if you're gluing acetate sections to styrene. Be sure to thoroughly roughen the areas to get bonded with 180 grit sandpaper.

 

 

[Khils]

Yes....an entailed project to say the least!

'57 Chev 210 4dr hardtop....well unless you know of someone whom has mastered & produced said body.

Was eye balling '56 Pont Starchier roofing....have not done anything yet. "KNOWING" the difference in plastics....

I had to ask my opening questions

BTW....Very impressed w/ your modifications.....coupe & fleetline.   Hats off!

[Khils]

Very helpful!!

Noted!! & very much appreciated THX!

[Mike999]

I saw this explained by some smart person on a military-modeling board long ago:  CA glue doesn't have much "shear strength."  IOW, the ability to move side-to-side without breaking the glue join.  Years ago, a TV commercial for super-glue showed a construction worker hanging from a steel beam, with his hard-hat glued to the beam.  A good stiff breeze and he could have been in serious trouble...

Anyway, that's where I learned to always use 2-part epoxy when gluing parts that might move or flex. I've been using DEVCON 2-part "Five-Minute" epoxy for many years. It's still sold at Lowe's, Home Depot etc.  If mixed right and allowed to set up hard, it makes a very strong bond.  While setting up, it does literally smell like a glue factory (or dead horse). But it's always worked for me. Other companies like Gorilla and Loc-Tite also make 2-part epoxies.

[Mark]

I wouldn't mess with combining acetate with styrene or resin.  Depending on storage/display conditions among other things, the acetate can still start warping at any time.  I'd hate to put a bunch of work into a conversion only to have it go wonky on me.  Too, the acetate often reacts with other plastics...ever see the fogged/cracked windows or plated parts on many of those old promos?  I'd either look for the needed piece in styrene, or make a mold and cast it in resin. 

[Ace-Garageguy]

A further note on epoxy...in general, the LONGER any epoxy takes to set up and cure, the STRONGER it will be.

I use a very high strength epoxy made for real aircraft, as I always have some in stock that's gone out of date and can't be used on real planes anymore...though it's still fine for anything else. It's $185 per gallon, so obviously most modelers aren't going to have access to it. It has to be mixed on a gram-scale, and takes several hours just to gel. It's 24 hours to reach handling strength, but to me, it's worth it. I NEVER have to worry about seams cracking.

HOWEVER, I have no use for 5-minute epoxy for anything other than jigs, fixtures, and things that won't ever be subjected to much handling or stress.

A 20-minute or 30-minute epoxy made for RC aircraft will be MUCH stronger than the 5-minute goo, and by virtue of being lower viscosity, it will BETTER wet-out any reinforcement material you might choose. The West-System 105 epoxies are very good too, strong, and are even certified for some light experimental aircraft use. They're available in reasonably-sized and priced quantities. Mixed with microballoons, they make an easy-to-sand lightweight filler with exceptional adhesion, for difficult situations.

And always bear in mind that epoxies need to be measured for mixing fairly accurately. NEVER be tempted to use more "hardener" to speed up the curing process. You will only RUIN the strength of the material by doing so.

Mark also has a very valid point about the possibility of continued warping going on with acetate parts, even after they're incorporated into a model.

It's not really hard to make molds of the parts you want to use, and make copies in fiberglass or resin which won't warp over time. The process of making silicone molds is thoroughly covered elsewhere on the web, so I won't go into that here.

The process of making partial molds from epoxy and light fiberglass cloth is shown in this thread of mine, restoring an old JoHan model. Though the particular model shown here is styrene, it's an older formulation that resists many solvent glues modelers have today, so all the replacement panels were attached with epoxy-fiberglass as well as being made from the stuff.

 

 

[Khils]

Thank you very much Bill....This is the avenue I will pursue .

 And Mark.....the thoughts of future warping.....I

A further note on epoxy...in general, the LONGER any epoxy takes to set up and cure, the STRONGER it will be.

I use a very high strength epoxy made for real aircraft, as I always have some in stock that's gone out of date and can't be used on real planes anymore...though it's still fine for anything else. It's $185 per gallon, so obviously most modelers aren't going to have access to it. It has to be mixed on a gram-scale, and takes several hours just to gel. It's 24 hours to reach handling strength, but to me, it's worth it. I NEVER have to worry about seams cracking.

HOWEVER, I have no use for 5-minute epoxy for anything other than jigs, fixtures, and things that won't ever be subjected to much handling or stress.

A 20-minute or 30-minute epoxy made for RC aircraft will be MUCH stronger than the 5-minute goo, and by virtue of being lower viscosity, it will BETTER wet-out any reinforcement material you might choose. The West-System 105 epoxies are very good too, strong, and are even certified for some light experimental aircraft use. They're available in reasonably-sized and priced quantities. Mixed with microballoons, they make an easy-to-sand lightweight filler with exceptional adhesion, for difficult situations.

And always bear in mind that epoxies need to be measured for mixing fairly accurately. NEVER be tempted to use more "hardener" to speed up the curing process. You will only RUIN the strength of the material by doing so.

Mark also has a very valid point about the possibility of continued warping going on with acetate parts, even after they're incorporated into a model.

It's not really hard to make molds of the parts you want to use, and make copies in fiberglass or resin which won't warp over time. The process of making silicone molds is thoroughly covered elsewhere on the web, so I won't go into that here.

The process of making partial molds from epoxy and light fiberglass cloth is shown in this thread of mine, restoring an old JoHan model. Though the particular model shown here is styrene, it's an older formulation that resists many solvent glues modelers have today, so all the replacement panels were attached with epoxy-fiberglass as well as being made from the stuff.

 

 

had that consideration also...YOU confirmed my veto!

[Mark]

In the early Eighties, I picked up a '60 Mercury convertible promotional model, molded in acetate.  This thing was really mint, nice and straight.  Not long after I got it, I was awakened in the middle of the night by what sounded like little pieces of plastic falling to the floor.  This thing had warped enough to "spring" one fender ornament and both taillight lenses. 

As of now, I have two acetate promos, both Continental Mark IIs.  They're sitting in a box in the basement.  I had thought about cutting the bodies apart and piecing them together to make a straight one long enough to pull a mold off of it.  Then I got a "mint" diecast Mark II for Christmas one year, and put that in the display case and never looked back. 

[bandit1]

  Sounds like you my have a very interesting project in mind.

A decent epoxy will give you a stronger bond than CA, and like any glued joint, the strength of the bond is in direct proportion to the AREA of the bond.

All this means is that a simple edge glued to another edge won't be very strong, and will tend to fail at the joint if you do any serious heavy bodywork...which I assume you intend to do if you're attaching large acetate sections to styrene.

Any way you can spread the bond over a larger area, or reinforce it, will be very helpful.

I do a lot of heavy parts swapping.

And I ALWAYS reinforce the backside of the joins with very fine fiberglass cloth, made for RC aircraft, and more epoxy. This is important to prevent cracking on styrene-to-styrene joints, and will be doubly important if you're gluing acetate sections to styrene. Be sure to thoroughly roughen the areas to get bonded with 180 grit sandpaper.

 

 

So hows that particular project coming along? havent seen anything new for a while

[Ace-Garageguy]

So hows that particular project coming along? havent seen anything new for a while

No time to work on models, period, for several months. I usually only log on here when I'm taking a short work-break, or in the evening when I just don't feel like going to the bench. I'm "retiring" sometime late this or early next year, so some models will very likely come out of hibernation.

[Art Anderson]

I wouldn't mess with combining acetate with styrene or resin.  Depending on storage/display conditions among other things, the acetate can still start warping at any time.  I'd hate to put a bunch of work into a conversion only to have it go wonky on me.  Too, the acetate often reacts with other plastics...ever see the fogged/cracked windows or plated parts on many of those old promos?  I'd either look for the needed piece in styrene, or make a mold and cast it in resin. 

The problem with "Tenite" (DuPont's trade name for the acetate plastic they invented in the late 1920's or so) has always been that it's  prone both to shrinkage and to moisture, which in the case of injection-molding, is very uneven, due to the "locked in" stresses that happen when liquified plastic of any sort is compressed into a set of hard metal dies under tremendous pressure (injection-molding machines do this with well over 100psi!), and once that acetate body shell is removed from the mold, the elements around it do start to come into play.   Ever see a cracked automobile steering wheel that was made anywhere from the late 1930's to the early 1960's?  Those were molded around formed steel units, and over time, the acetate plastic would shrink, leading to noticeable cracks in say, the rim, sometimes even in the spokes.   About the only acetate promo's I have acquired which have no warpage are those I've bought way out west, such as NNL-West, even GSL, where the air is dry, which allowed the acetate to "settle" (or whatever!) without humidity.

Why acetate plastic, you might ask, in those promotional model cars of the 50's?  The simple, and plain answer is that "plastic" had a very bad reputation then--early styrene was hard,  and as brittle as glass--when it broke or shattered, the shards were as sharp as glass--lots of little kids back then (and I was a little kid in the late 40's-early 50's) got cut fingers from broken, cheap styrene plastic toys.  For this very reason, most quality plastic toys (and promo's WERE seen as toys!) back then were molded in acetate plastic, for the simple reason of SAFETY.

But, what about early model car kits?  Only a few kits were ever molded in acetate--Monogram's very first model car kits were first shot in acetate, but once they realized they were not making toys, but something just a bit more serious--styrene.  When AMT Corporation came up with the idea that really put them "on the map", that being their precedent-setting 1958 "3in1 Customizing Kits",  they wisely went to styrene, even though it was a fairly brittle material,  but with the material thickness of the body shells and chassis, they did survive a lot of handling.

About 1960, ABS plastic (I'm not even going to attempt to type out that name in full text!) came on the scene, and by 1962 or so, all promotional model cars were being made from ABS--AMT, JoHan, and by 1965, MPC.   ABS had the toughness, and shatter-proof qualities of acetate, but the stability (warping resistance) of styrene, and can be far more easily bonded to a polystyrene part today.  On the flip side of all this about acetate promo's,  I have a gorgeous '57 Chrysler Windsor that Dean Milano did almost 40 yrs ago--and it's still straight as a die, to this very day--so not all acetate promo's (this model was done from an acetate promo) warp--but that's a very random thing.

 

[Ace-Garageguy]

 

Why acetate plastic, you might ask, in those promotional model cars of the 50's?  The simple, and plain answer is that "plastic" had a very bad reputation then--early styrene was hard,  and as brittle as glass--when it broke or shattered, the shards were as sharp as glass--lots of little kids back then (and I was a little kid in the late 40's-early 50's) got cut fingers from broken, cheap styrene plastic toys.  For this very reason, most quality plastic toys (and promo's WERE seen as toys!) back then were molded in acetate plastic, for the simple reason of SAFETY.

...I have a gorgeous '57 Chrysler Windsor that Dean Milano did almost 40 yrs ago--and it's still straight as a die, to this very day--so not all acetate promo's (this model was done from an acetate promo) warp--but that's a very random thing.

 

A couple of thoughts to follow Art's...

Old timers (like me) will probably remember seeing the phrase "molded from high-impact styrene" or something similar. As knowledge of plastic chemistry grew, the initial problems with brittleness were worked out. But many of the earlier formulations are SUPERIOR to what we're getting today in terms of chemical resistance. Some of the early styrene kits from Johan (I speak from experience here, having late '50s kits in stock) are so resistant to solvents that it's difficult to glue them together with today's liquid cements. This has an upside, however, in that they DON'T CRAZE when sprayed with a very wet coat of "hot" automotive primer like SEM or recent Duplicolor formulations. Unfortunately, much of plastic engineering peaked some time ago as to "better", and the focus of much reformulation now is towards "cheaper", which is why observant and long-seasoned modelers are noticing problems using "hot" primers that worked exceptionally well for many, many years.

As far as the shrinking and warping of old acetate models goes, it does indeed appear to be random, but as Art mentions, models stored in very low humidity conditions are far less likely to be adversely affected, and this is also true of other early synthetic materials and fibers. I would suspect...though I cannot claim to have done any experimentation to verify this...that if acetate parts are coated both inside and out with a vapor barrier like paint (or epoxy on the backside) they will most likely be immune to atmospherically-induced degradation.

[Bob Ellis]

I have an acetate promo that was heavily spray painted and little warp. The air may be a problem. Sealing the surface with paint helps it seems

A plastic called Cycolac was introduced in mid-1961. Half of the AMT promos warped like crazy, while others remained straight. 

[Ace-Garageguy]

I have an acetate promo that was heavily spray painted and little warp. The air may be a problem. Sealing the surface with paint helps it seems

A plastic called Cycolac was introduced in mid-1961. Half of the AMT promos warped like crazy, while others remained straight. 

The first line is very interesting.

"Cycloac" was a trade name for a particular formulation of Acrylonitrile Butadiene Styrene, the ABS that Art mentions above.

In a way, you can think of it as 'super-styrene'. It has superior strength and other properties to "styrene", and is widely used as the material of choice for common objects all around us, like many interior parts of cars, computer, phone and power tool housings, frames and supports for the internal parts of copiers, etc. It's also used as the filament in one type of 3D printing, and Legos.

It DOES dry out and become brittle (even crumbling) over time if it's exposed to moderate heat continuously (or prolonged thermal cycling), as anyone who's ever worked with electrical connectors under the hood of an older electronically fuel-injected car has certainly noticed. It also degrades in UV light, which is a constituent of of sunlight.

As well as being tougher than "styrene", and vastly more dimensionally stable than acetate, ABS is also more solvent-resistant than "styrene". It takes a "hotter" solvent to glue it to itself than the typical model-quality styrene, though epoxy works well on it.

Edited September 6, 2017 by Ace-Garageguy