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Paint formulae have been changing over the last two decades. We are lucky we can still paint stuff. Automotive acrylic enamel used to be my favorite, but prices have jumped 100 fold, and quality is nowhere near as good. I am not skilled enough to spray the new water based stuff.
Older model paints would last in the jar until you used them up or they turned rock hard. Modern paint has a shelf life of under a year once it is opened. I have some Testor's PLA that says 19 cents on the lid - still good after a half- century.
Even my ex- favorite Krylon has become basically unusable.
Woe!
If it's still giving off odor, it hasn't fully cured. How to speed it up? I dunno.. enamels usually speed up if you bake them*.
*I assume no responsibility if you melt your model
the operative word is patience, until the paint dries out.
Put the model out in the sun the UV rays will speed up the curing process.
Originally Posted by PRR Man:
the operative word is patience, until the paint dries out.
That my method as well....the smell eventually dissipates, but it will seem like forever especially if your waiting for it to do so.
Bob
Patience, David. It'll go. Smart thing putting it outdoors. But in the sunshine? I'd be afraid the plastic would warp. 
Bob2 - Your note made me smile. I still have some useable Testor's PLA from that era as well. And I have some Humbrol enamel that I know goes back at least as far as 1959 - still using it!
Originally Posted by TrainsRMe:
Patience, David. It'll go. Smart thing putting it outdoors. But in the sunshine? I'd be afraid the plastic would warp.
Bob2 - Your note made me smile. I still have some useable Testor's PLA from that era as well. And I have some Humbrol enamel that I know goes back at least as far as 1959 - still using it!
How do you know the model is plastic??
You might consider assembling a couple of light bulbs in a box to build an oven of moderate temperature - put a dimmer control on it for temperature control.
Could also set it on the A/C vent to keep air moving over it.
Could set it outside in indirect light.
Originally Posted by mwb:
You might consider assembling a couple of light bulbs in a box to build an oven of moderate temperature - put a dimmer control on it for temperature control.
Could also set it on the A/C vent to keep air moving over it.
Could set it outside in indirect light.
Yes. fabricate a drying box. Some of the foam insulation with the foil face for the interior. A basic light socket for a small wattage incandescent bulb.
Then ventilate it. Radio Shack has a small 4" inch fan, similar to a computer fan that operates on house current. Moves a lot of air.(65cfm) The 4" inch size is key. You can then use dryer vent parts to create the exhaust duct.
It could double as a small spray booth also.
My wife is an odd bird, she likes the smell of paint, she loves the smell of gold paint that comes in a spray can.
She like french cheese also. all that said she lets me buy trains so...
Originally Posted by DaveJfr0:
I didn't think of making a controlled "oven" so to speak, so I will look into doing that, but I am weary of investing a lot of time in a one-time use device.
I've had one on/off and made it so it would fold & collapse for storage. It was useful for spraying "stuff". And, when it looked like it was going to be stored for a long time, salvaged the bits & bobs and trashed the rest. Cheap and disposable, and easy to make a replacement when needed.
Dave, Save the oven for the winter. Just put it out in the Sun. It won't warp and the breezes will help.
Pete
Dave
My standard paint/decal/modeling putty/wet leaves/ drying technique is to put the model under a cheap gooseneck desk lamp with a 100-150 Watt floodlight. I just put the thing on my workbench.
I have yet to melt anything, bubble a surface, or start a fire. Your results may vary
....a cheap gooseneck desk lamp with a 100-150 Watt floodlight. I just put the thing on my workbench.
Can also be used to make cookies in your Easy-Bake oven, 
I avoid enamels if at all possible. I find that even months later they can be soft and easy to damage.
No matter what paint I do use I always cure the paint in my food dehydrator. You can make a 'paint oven' but my dehydrator was $9 and has served me for almost 20 years. Hard to make one for that price. Plus it sits out on the kitchen counter....try that with a home made box!!
I can paint in the morning and decal that night.....and been doing this for 20+ years without an issue. Hit me offline if you need more info. THX
Never thought of using a food dehydrator. Great idea, thanks for posting it.
Internet post:
"Technically speaking, enamel doesn't dry, it cures. It's a fundamentally different process.
Paints like nitrocellulose lacquers (like automotive lacquers) and aqueous acrylics truly do dry. The binder of these paints is dissolved into solvent (either lacquer thinner or water), and the paint hardens as the solvent evaporates.
Dehydrators can be very effective in driving off solvents- they're obviously designed to evaporate water out of food, and evaporating solvents is very similar.
Enamels harden due to oxidative crosslinking. When enamel is exposed to oxygen, it starts a chemical process which molecularly hardens the binder- creating a sort of 'shell' as binder molecules link with each other. Heat and convention have a limited effect in speeding this process. I may increase the crosslinking process slightly, but certainly not in the way that it dries solvent.
If you thin enamels with lacquer thinner, you're not changing the curing time. By introducing a volatile solvent, you're creating a mix that needs to cure and dry. But after the solvent has finished evaporating, the enamel binder still must cure- and the binder will still cure at it's own pace.
If you want enamel to cure quickly, the best way is to spray it as thin as possible. This way as much of the paint as possible is exposed to oxygen, and it can all go to work on curing. If you apply enamels thickly, only the outside surface is exposed to oxygen, which can dramatically increase the curing time of the paint deeper in the layer. Spray enamel too thick and it is possible to keep some of the paint from ever completely curing. The outermost portion exposed to air can cure perfectly well- but this cured outer portion becomes a barrier to prevent the paint deeper in the layer from being exposed to oxygen. As a result the paint will always be soft, under a thin cured film.
This is why enamels have such strange application instructions- you must spray everything on at once (within a couple of hours), or you must wait days or weeks to apply another layer. If a layer is applied and it begins (but does not complete) curing, only to be covered by another layer, the first layer will never cure.
Of course applying many thin fully cured layers is a perfectly acceptable (if very time consuming!) way of applying enamels. But if you try sanding/polishing it, you will see quickly that each of these individually cured layers is distinct. You will clearly see where you've sanded through one to the layer below, rather like sanding through an onion. It makes enamels difficult to apply thickly...."
Paints like nitrocellulose lacquers (like automotive lacquers) and aqueous acrylics truly do dry. The binder of these paints is dissolved into solvent (either lacquer thinner or water), and the paint hardens as the solvent evaporates.
Dehydrators can be very effective in driving off solvents- they're obviously designed to evaporate water out of food, and evaporating solvents is very similar.
Enamels harden due to oxidative crosslinking. When enamel is exposed to oxygen, it starts a chemical process which molecularly hardens the binder- creating a sort of 'shell' as binder molecules link with each other. Heat and convention have a limited effect in speeding this process. I may increase the crosslinking process slightly, but certainly not in the way that it dries solvent.
If you thin enamels with lacquer thinner, you're not changing the curing time. By introducing a volatile solvent, you're creating a mix that needs to cure and dry. But after the solvent has finished evaporating, the enamel binder still must cure- and the binder will still cure at it's own pace.
If you want enamel to cure quickly, the best way is to spray it as thin as possible. This way as much of the paint as possible is exposed to oxygen, and it can all go to work on curing. If you apply enamels thickly, only the outside surface is exposed to oxygen, which can dramatically increase the curing time of the paint deeper in the layer. Spray enamel too thick and it is possible to keep some of the paint from ever completely curing. The outermost portion exposed to air can cure perfectly well- but this cured outer portion becomes a barrier to prevent the paint deeper in the layer from being exposed to oxygen. As a result the paint will always be soft, under a thin cured film.
This is why enamels have such strange application instructions- you must spray everything on at once (within a couple of hours), or you must wait days or weeks to apply another layer. If a layer is applied and it begins (but does not complete) curing, only to be covered by another layer, the first layer will never cure.
Of course applying many thin fully cured layers is a perfectly acceptable (if very time consuming!) way of applying enamels. But if you try sanding/polishing it, you will see quickly that each of these individually cured layers is distinct. You will clearly see where you've sanded through one to the layer below, rather like sanding through an onion. It makes enamels difficult to apply thickly...."
Old Goat
What you copied is of course quite correct, and you need to worry about that, particularly in automotive applications. But for models, generally if the enamel coats are too thick to cure properly, they also tend to be thick enough to hide the surface details. And I doubt an experienced modeler like Dave would have done that.
I have painted model cars with thick "wet" coats of Testors spray enamel in order to produce a smooth glossy finish
Since this was your initial experience with enamel paint, mixing and applying the paint to scrap styrene as a test would be best...as well as painting in a suitable (low humidity, moderate temperature) environment. A paint booth is a wise investment. Practice, practice...blah, blah, blah.
From the Testors website:
Fine detail airbrushing requires practice and varies greatly with the equipment and air pressure being used. Experiment on scrap material before you begin painting an actual project.
Gloss; 3 parts paint to 2 parts thinner.
Flat; 3 parts paint to 1 part thinner,
Air pressure setting should be around 20-25 PSI.
Enamels require 48 hours for a full cure.
Thinner: - all Enamel solvents
We do not recommend that the enamel paints be placed in any oven or kiln at any temperatures, due to performance and safety issues, ie; Enamels are considered Flammable/Volatile materials and do have a flash point. We also do not recommend the baking of the Acrylics, which are certified non-toxic, however they were never designed with the idea of baking in mind and we cannot be held responsible for the outcome.
...and it's entirely possible for you to contact the good folks at Testors, explain your project with the exact steps used for painting and hear what they recommend.
Styrene and Polystyrene derivatives (ABS) have a melting temp around 200 to 212 F
If you live in the desert and leave it in a closed automobile than you may have an issue, but if you put it out on the deck for a couple of hours and around 4 or 5 pm you should be OK. Just keep it out of the acid rain! 
Originally Posted by Moonman:
Then ventilate it. Radio Shack has a small 4" inch fan, similar to a computer fan that operates on house current. Moves a lot of air.(65cfm) The 4" inch size is key. You can then use dryer vent parts to create the exhaust duct.
It could double as a small spray booth also.
I sincerely doubt that a fan moving 65cfm will sufficiently vent a properly sized booth to paint an O scale car or loco.
Better to read the info in the 11th post in this thread:
Originally Posted by Old Goat:
I sincerely doubt that a fan moving 65cfm will sufficiently vent a properly sized booth to paint an O scale car or loco.
Better to read the info in the 11th post in this thread:
That was a good read. I am thinking of building a down draft booth and this was good info. Thanks
Dave, I use Model Masters Dark Flesh Tint paint for my trucks and couplers, I also use it for box car underframes. Now to your issue, do you use Testors, or Floquil thinner with it? If you use another brand thinner (or lacquer thinner) this may be your problem. Model Masters paints require their own thinner, or you can/ will get glazing, and a prolonged cure time with the awful stench. I thin my paint only about 10%, and get great results, with a cure time of no more than 3-4 days. Often times much less. Usually my basement will stink for a day afer painting, but that is all.
The old (1970s era) Floquil paints could be thinned with good old plain lacquer thinner, but the new stuff can't. Same with Scalecoat. Also, make sure you paint is very thoroughly mixed, I know this sounds redundant, but I've had paint that seems to take forever to get mixed properly. And Model Masters paints are one of them! Good luck!
Lacquer thinner dissipates in a day or two. Mineral spirits take much longer. I am surprised you didn't craze the plastic using lacquer thinner.
Pete
David, I'd be willing to bet that lots of us learned something on this thread along with you. 
Originally Posted by DaveJfr0:
I know I can sand off the slightly rough surface...
Originally Posted by Norton:
I am surprised you didn't craze the plastic using lacquer thinner.
Pete
Pete
Bingo.
Originally Posted by DaveJfr0:
There's the crux of my problem. I used some brand of lacquer thinner from walmart...
Oh well, so much for your statement: the 48 hours is a lie for curing.
Dave,
This info, from the Testors website, should save you a bit of time for the next step in your project:
Enamel Paint Removal
To remove dried enamel film you may use PollyScale Easy Lift Off Remover No. F542143. Please see instructions above under the Acrylic Removal section.
You may also use...(attention Wal-Mart shoppers)...Easy-Off Oven Cleaner. We recommend the Fragrance Free version of the product. The procedure for removal is the same as the above one for PollyScale Easy Lift Off Remover or ELO.
The Testors FAQ section contains lots of good information.
Simply amazing. 
Originally Posted by DaveJfr0:
No matter how this project shakes down…I'm done with enamel and will do what I have to do to mix the color I want in acrylic. At least having posted here will provide caution and details to whomever runs across this post and wants to paint with the same brand in the future. It'll come up in a google search just like I found the other forums.
I'd not give up on enamels for acrylics. Acrylics have their own issues. When good hobby acrylics became available about 20 years ago I dove right in. I was going to go all acrylic and dump my enamels and lacquers. I used the acrylics on a few plastic models and they looked great. A new age had arrived.
Until about 3 months later when the first few models I had done started being covered with spiderweb cracking. When I inquired to the manufacture about the issue they told me I had painted the 2nd color too soon (it was a 2 tone car) and also had applied decals too soon. I needed to allow the paint to gas out for 5-6 weeks before a 2nd coat or color.
I went back to my solvent based paints that week. Enamels with mineral spirts will work well for model work. Lacquer is better but getting harder to get.
On the dehydrator......on mine I cut two rings trays out. You do not want to get too close to the heating element. On items that will not fit down into the rings I leave the top off and rest the model on the top ring. This will allow the dry heated air to rise and heat the entire body. If needed I can place one end in then the other. 30 minutes for lacquer and 90 minutes for enamels.
If the humidity was too high when the finish was applied moisture in the air got trapped in the film stopping the interior curing process before the surface cured.
At least if you can still smell the paint the process is still continuing but it could literally take months.
As noted enamels cure not dry like lacquers. Because you used a lacquer thinner it evaporated before the curing process could be initiated throughout the film.
Dave, the problem is not enamel paints. If you had used the correct thinner you would not have had excessive odor and the paint would not have attacked the plastic. Lacquer thinner is not appropiate for any of the modern model paints I know of. Save it for cleaning brushes and stripping metal models but not for paint mixing.
Pete
Originally Posted by DaveJfr0:
...I just went to take a whiff of them and they still have the same smell. Do you have an answer for that one too?
Since you have the tendency to omit crucial information from your posts or ignore requests for details:
BEFORE working on your model => Read and follow the manufacturer product instructions/warnings, check their website for a FAQ section and practice on scrap material.
Hope the project works out for you.
What do you folks think of Tru Color paints? All the ads about it say solvent based. Anybody have any luck with it?
I missed that part where he used lacquer thinner in the enamel. I did that over a half- century ago on some parts on my Ford Convertible. They remained sticky for a month! Use enamel reducer for thinning enamel, and you will probably be dry in two days.
Thinner can be critical - I have used lacquer thinner in Floquil with success, but not with their clear - I found Dio-Sol to be absolutely necessary with the clear coat and Dull Cote.
They say you can use Lacquer thinner in Scale Coat. Never had the courage to try.
Originally Posted by CRH:
What do you folks think of Tru Color paints? All the ads about it say solvent based. Anybody have any luck with it?
I think that the jury is still out.
Some one sent me a copy of the MSD on their thinner and as I recall it was rather similar to the components of Dio-Sol although I don't recall whether the proportions were close or not.
This past year I switched from Floquil after it was bought out by Testors and the formulation change. I am now using Scale Coat II and Tru-color exclusively. I love them both and am getting very good results because they are both solvent based and I am used to that type. I use the recommended solvent for each without compromise, expensive, but no problems.
I gave away over 200 bottles of Floquil to a couple of friends. They are happy and so am I.
Ben Brown
I also meant to mention that one additional reason I like Scale Coat II by Weaver is that it is available in four different packages, 1oz., 2oz.,spray, and paint pens.
Ben Brown
Originally Posted by Ben Brown:
I also meant to mention that one additional reason I like Scale Coat II by Weaver is that it is available in four different packages, 1oz., 2oz.,spray, and paint pens.
Ben Brown
I've tried ScaleCoat II and didn't like it...takes too long to dry and sprays like Alkyd enamel...bleh...I'll take synthetic paint anyday.
Originally Posted by mwb:
Originally Posted by CRH:
What do you folks think of Tru Color paints? All the ads about it say solvent based. Anybody have any luck with it?
I think that the jury is still out.
Some one sent me a copy of the MSD on their thinner and as I recall it was rather similar to the components of Dio-Sol although I don't recall whether the proportions were close or not.
I've had good luck with Tru-Color paints and it's predecessor, Accu-Paint. The two are close if not identical.
Dries smooth, quickly and can be masked within a half hour. Leaves a good, semi-gloss surface that can be decalled on. Floquil and Dullcoat can be sprayed over it with no issues.
But there is a learning curve, it requires a slightly different technique as by my observation doesn't come out in as wide a spray pattern as Floquil, more air pressure and the lighter colors will require a gray primer or more coats than Floquil.
Rusty
Over on the Model Railroader Magazine web site there was a post in the comments section by Tom Piccirillo, President Micro-Mark, with regards to the recent Testors announcement.
THOMAS PICCIRILLO from NEW JERSEY said:
Here is the link to article; you'll have to weed through the comments to find the comment I am referring to above.
Scott Kurzawski
Austin, TX
Micro-Mark is working on it, and shortly (by early Fall 2013) we'll have a superior-quality water-based ready-to-spray acrylic in at least the more-popular generic colors, such as Rail Brown, Grimy Black, Aged Concrete, Clear Flat, etc.
This paint can also be applied on wood with a paint brush.
We are a distributor, so your dealer can contact us, as well.
Tom Piccirillo President Micro-Mark