Warning, a new concern replacing "Tire Burn"

[Oldcarfan27]

I just recently opened this older (90's issue) Monogram '70 Trans Am kit to build. The inner bags were still sealed and I purchased the kit new way back when, so I know how it was stored - Indoors in my spare room.

However,  when I opened it all up, I found small burn marks on the drivers door. Right where it was resting against the inner bag.

It's not major, I can sand it out, but it does raise the concern - We used to have to isolate the vinyl tires from the plastic to avoid "Tire Burn". Now I have to wonder if the BAGS they came packaged in can also do the same damage!

Has anyone else had this issue happen to them? If so what did you do to resolve it? Is anyone else concerned about this problem? How are we going to know what plastics have what effects on other plastics while in storage?

[SfanGoch]

It's a crapshoot. Since model manufacturers have, and will continue to use their own particular polystyrene and vinyl formulations obtained from various sources, you'll never really know. 

[Roncla]

Thats opening a can of worms and something else to worry about when storing our stash. I wouldn't be surprised if the plastic bags varied in composition as much as the kits do.

[espo]

This looks to me as if this model has been exposed to a high heat situation at some point in time. From what you're saying the storage since you have had it would not cause this to happen. So it just may be that from the time it was created, packaged, shipped to the warehouse, and then the retail point it may have been stored in such a way that the wrapping melted to the body.   At least you can correct it with little effort and that's a good thing.   

[Oldcarfan27]

5 hours ago, Roncla said:

Thats opening a can of worms and something else to worry about when storing our stash. I wouldn't be surprised if the plastic bags varied in composition as much as the kits do.

Yep, that's my point. What if the BAGS contain the same chemicals as the tires! Now we're going to have to check our stashes for the very thing we thought was protecting them!

[Snake45]

I've seen this "bag burn" on the paint of completed models, but don't think I've ever seen it on raw plastic. Interesting.

[Tom Geiger]

and be careful storing your models in packing peanuts.  They will also cause problems over time.  Especially the ones that are designed to break down and return to the environment.   

Remember, none of this was ever designed for stability over long periods of time.  Model manufacturers sold a product that was supposed to be opened and consumed.  

[Lizard Racing]

So I suppose if a kit is to go into long-term storage, the sprues should be wrapped in paper (?) and isolated from anything vinyl.

Anyone have ideas for long-term storage?

[SfanGoch]

3 hours ago, Oldcarfan27 said:

Yep, that's my point. What if the BAGS contain the same chemicals as the tires! Now we're going to have to check our stashes for the very thing we thought was protecting them!

The plastic bags are made from polypropylene, which is stable and doesn't leach any chemicals. That's why it's used for ziploc food bags, food containers, etc. The chemicals used to make the tires cause an exothermic reaction when they leach out of these molded tires, generating heat. This is what "tire melt/burn" is. Even if bagged separately, the heat generated is strong enough to melt any polystyrene it come in contact with without damaging the polypropylene packing bag. 

[SfanGoch]

34 minutes ago, Lizard Racing said:

Anyone have ideas for long-term storage?

Open all of your kits, remove the tires and place them in ziploc bags, mark the bags with the pertinent kit info and store them in a cool, dry container. If that seems like a lot of work, well......they're your kits. I've done this and it amazes me how many sets of soft "rubber" tires deteriorate to the point that they literally fall apart into sticky, messy blobs similar in consistency to a melted Gummi Bear.

[ZTony8]

I have several sets of the old AMT supplied Firestone Supreme narrow stripe white wall tires stored in plastic drawers. Some have started to "melt" (mildly) and lightly stick to the drawer while others in the same drawer have not. And some of those tires have gotten hard over the years. It seems very random.

[NYLIBUD]

I have long termed stored a lot of different plastic models in my life,both as a kid,and now as an adult.And upon opening them,I have NEVER had this kind of issue with things warping,or melting,etc.It could just be possible that the kits are not being stored in a enough of a cool,dry,dark environment.I don't know,I never gave it much thought until reading this post.Very interesting however.Hmmmm

[SfanGoch]

Polystyrene  is a durable polymer. If the kits are stored at temps below 90° F, there won't be any warping of the parts. Most warping occurs when the parts trees are ejected from the molds before being allowed to cool down properly. The tire burn phenomenon seems to be random. I have three Johan 1931 Cadillac Cabriolet kits. one has tire burn on the top of the convertible roof and on the top of the right front fender. The tires fit the shape of the burn marks; however, none of the tires exhibit any melting or deformations. They all are in perfect condition. Go figure.

The stock tires included in the Revell 85-4295  '55 Chevy Belair HT I have were sticky, blobular lumps still attached to the tire sprue; and, this was a new, factory sealed kit. I requested replacements from Revell but was informed the kit was OOP. Yeah, so? It has the same friggin' generic tires used in every 55-60 Chevy kit they make.

[Snake45]

4 hours ago, SfanGoch said:

Polystyrene  is a durable polymer. If the kits are stored at temps below 90° F, there won't be any warping of the parts.

It'll take more than that. For years I stored all my kits and many of my builtups in an attic that would get on high side of 120* in the summer with no warpage or problems at all.