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Kang

Does Tamiya primer just not like squeaky-toy rubber or what?

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Pretty much as the thread title says, though to be more specific it is Tamiya Fine Surface Primer (white).

 

Converted a rubber squeak-toy for a mini I need for my D&D campaign. (Sorry, no pix yet but I will post something in WiP eventually once I get time to set up for photos.) I filled the hollow interior of the squeaky-toy with plaster so the problem is not that it is flexible, because that is no longer the case; the primer just never fully dried. Even after several weeks, it feels a bit sticky and I get primer on my fingers if I hold onto it for a minute or so. Note, when I sprayed the primer on it was fairly humid; just didn't have any other option this summer as it's been raining pretty much every day around here. But I suspect it is mainly an issue of the primer's reaction to the rubber rather than a humidity issue.

 

So last night I tried to apply a thin glaze over bare primer as per Lunchbox's recent tutorial thread, but it just beaded and rolled off! Thicker paint worked better, but by this morning it had all sort of cracked so that now there are zig-zagging lines of primer-white running all over it. I guess this is because the primer didn't dry properly... Though I should mention this did not happen on the sections where primer is covering green stuff, where the primer seems to have dried better.

 

I think I might try giving it a shot of Dullcote tonight when I get home; maybe once that's dry (if it doesn't have a bad reaction to the primer), I can paint over that without having this problem.

 

Anyone else ever see this happen, or have any idea whether I'm right or wrong about it being a matter of the primer not liking the rubber or whether the Dullcote idea is likely to work? I'd appreciate any suggestions.

 

Thanks,

 

Oh, and while I'm at it, does anyone have any suggestions for a cheaper way to do a water effect on the base than buying that expensive Envirotex stuff or what have you? So far I'm working with thin layers of white glue and Delta Ceramcoat gloss varnish, but it's incredibly time-consuming and less transparent than I'd like with any kind of thickness. If I maybe pour on some Future a few mm deep (appx 1/8 inch or so), does anyone know if it would dry to a fairly smooth surface?

 

Thanks again,

 

Kang

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I had a rubber skull do the same thing, and even 5 months later it still never dried. I don't know what the specific chemical problem is, but it's like the undersurface leaches oils into the enamel. Acrylics didn't do much good either, they'd quickly clump or bead. If I did manage a decently smooth coat it would eventually flake off. The skull was just display, it wasn't being handled.

 

I also tried dullcote, and it reacted the same way so it was completely unpaintable. I don't have any solutions to offer, but I have had the same kind of problem.

 

****Edited to add: This was all before I started playing with future, though. If I was messing with it now I might dip the whole thing in Future and see if that took. If that gave a decent solid surface, then I'd try priming over that. If you can get something to act as a barrier between the rubber it might work.

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The more flexible the polymer, the more plasticizers it has. Since paint binders are also polymers...the leaching plasticizer will likely keep it from curing properly. Makes sense to me, but I haven't plaid around with bendy stuff enough to know for certain.

 

I have used a mineral oil bath in order to leach the plasticizers out of bendy plastics and rubbers before. It accelerates the natural process - and might be worth a try for you in this case. Fill a jar with mineral oil, toss the toy in so that it is submerged...put the lid on. Let it sit for a week or so, take out and rinse and wash to remove any surface residue. The surface should feel less rubbery. Give it a paint job and hope for the best.

 

The science involved says it should work...but like I said, I haven't played around with the bendy stuff enough to know for certain.

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Well, it's already got primer all over it so painting right on the rubber is no longer an option unless I strip it, and I'm concerned that Future might not act that much differently than my paint has. Maybe I'll grab some of that mineral oil and try Joe's idea first if I can figure out where to find some, though a week is a long time to wait. Especially since I've been sort of subtly stalling the PC's for a couple of weeks anyhow already, lest they encounter it before it is painted...

 

Joe, does your chemistry-infested brain know if ordinary spray paint from a cheap rattle can might stick to this without using the mineral oil bath? Or would the polymer thingy be an issue again like it was with the primer? The mini is going to be mostly all one colour to begin with anhow, so that might not be a bad idea even if I wasn't having this trouble. I'm basically hoping to find a shortcut here if possible.

 

Thanks for the tips so far,

 

Kang

 

Oh, PS. Since Froggy, the infamous master of conversions, has replied, I might as well mention that the squeaky toy is, er, was, originally a frog! Now it's been converted to a froghemoth (based on the illustration in dungeon magazine #128), which is I guess some sort of distant cousin. ::D: Small world, eh?

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Krylon makes a special bonding spray paint that supposedly "becomes one" on a molecular level with plastics. It's called Fusion and that *might* work for you. It can be found at Wal-Mart and most other places that carry Krylon products.

 

Of course, before doing anything else you're going to have to get the old primer off. If it's still wet that might not be too difficult.

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Yeah, Krylon Fusion works by cross linking with the underlying polymer. Works well enough on most plastics - though I haven't used it on any rubbers (though most rubbers are actually plastics...but that starts to get a bit more complicated).

 

As mentioned already though, since you already have primer on it, you will likely need to remove that before you go any further. I don't have my Tamiya MSDS book here in the shop though, but if they use a hexane compound in the thinner - it might not help even if you remove the paint that is already on it. Hexane likes to attack organic rubber compounds...so if the toy is made out of organic rubber and you brought it into contact with the hexane in the spray...perpetual stickiness...sort of.

 

Taking a quick flip through my books though - there are a few different curative methods which you might try. Oxygen rich environments can be used to stabilize the compounds. The free molecules bind to the oxygen atoms - though it can lead to a powdery paint. Heat curing can also accelerate the bonding if it isn't a different issue. The heat curing can be achieved at relatively low temperatures (125-150 F) although higher temperatures provide a more pronounced effect - granted those higher temperatures might cause problems with the rubber itself. The heat helps to deal with hexane attacks on organic rubber as well.

__________________

 

Missed the second question the first time...

 

Oh, and while I'm at it, does anyone have any suggestions for a cheaper way to do a water effect on the base than buying that expensive Envirotex stuff or what have you? So far I'm working with thin layers of white glue and Delta Ceramcoat gloss varnish, but it's incredibly time-consuming and less transparent than I'd like with any kind of thickness. If I maybe pour on some Future a few mm deep (appx 1/8 inch or so), does anyone know if it would dry to a fairly smooth surface?

 

Future is a bit thin for doing deep pours - normally you will want to use as thick of a medium as possible when using one part compounds for water. Since they usually cure as a result of evaporation...the more thinner that will evaporate, the more shrinkage you will have to deal with - and shrinkage is bad. It will still produce a more or less smooth surface, and you can build it up in several layers to get to a descent thickness. The same applies for most other varnishes.

 

There are several gloss gel mediums which you can apply thicker in each pass - some are less expensive...others get pretty pricey. The least expensive compounds are ones which you find in industrial and commercial sections of stores. A product called Bar Coat normally costs about half Envirotex...and it is basically the same product. It is used for doing the thick gloss coats on bars and tables...especially those table tops you see at some restaurants that have the coins and stuff embedded in it. Another product can be found at automotive supply stores. It is used for doing FRP work, and it is a 2 part polyester resin. Again, cheap and works well enough. There are normally two types of polyester resin at most stores, one clear and one yellow. The clear costs more than the yellow...but both work well enough for water depending on the circumstances (it isn't an opaque yellow - more transparent).

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When painting plastics (and rubbers in there various forms) there are two things which are normally the cause of problems. The plasticizers in the items itself, and the chemicals in the paint. One of the two will almost always be the source of problems with the paint sticking or curing properly. Tracking the exact source down can be a bit trying - and figuring out how to fix it the fastest can be even more of a pain.

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Wow, thanks for all the great tips! Perhaps unfortunately, I jumped the gun a bit and went out and picked up some spray paint for plastics and gave it a shot before seeing anything posted after my last entry in this thread.

 

Checked it this morning - the paint didn't crack. I still have to check if it dried properly though; was too scared to touch and check for stickiness before leaving for work today in case I would have discovered I'd made an even bigger mess of things. I'll give that a try tonight and get back Monday at the latest to let you guys know how it went. Keeping my fingers crossed - I still have to convince some colours other than green to stick on this mini, although they're mostly over the green stuff areas where the primer seemed to go on fine, so that should be OK too... I'm hoping.

 

Wound up pouring on some Future too, for the water effect. Seems to be working nicely, and although it has to be poured in layers, the layers can be a lot thicker than the stuff I had been using before that. It does shrink a little as it dries, although it does so nice and evenly. So I guess I'm just going to have to sand down & recoat the raised edges where it sort of crawled up the sides of the Lego I'm using to contain it on the base, and maybe on the edges if the places where one Lego block meets another are visible, once the Lego frame comes off. Still better than keeping on having to paint on paper-thin layers of Delta gloss varnish, then carve half of it back off the next day when the shrinkage has caused air bubbles and whiteness...

 

Thanks again for all the tips and suggestions!

 

Kang

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OK, so the spray paint I tried didn't really dry all over either, though it did end up a little better than the primer layer. Not sure if it's because I used the "for plastic" spray or because I've got enough layers on that the still-sticky parts & plasticizers are sealed below enough semi-dry layers to let the top layer dry... for the most part... for the time being. Maybe I could douse it with more plastic paint and get it even better still, but who knows if it would stay that way, plus this is just getting ridiculous. So I'm going to try and give the mineral oil dip a whirl and just hope waiting while it soaks up all those nasty plasticizers isn't the reason the mini won't be ready when the party encounters the monster it was created to represent.

 

But I know nothing about the stuff... I googled it and apparently you can often find it at the drug store. Seems like it has a million different and videly varied uses though - so I'm wondering if anybody has any suggestions for where I might get the best price on enough of it to soak a rather large mini (ie. bigger than my hand) in, if not at the drug store? I also read that baby oil is simply mineral oil with a little bit of perfume added in. If I'm having trouble finding a product just marked, "mineral oil", can I assume that isn't just BS and use baby oil instead, or would the perfumes they add to it mess up my results? I can live with a mini that smells nice, but not if it interferes with my painting!

 

Thanks,

 

Kang

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I think you should be able to find big value-sized jugs of mineral oil in large department stores like Wal-Mart (or its equivalents) in the paint sections.
So, to follow up on this, I tried Wal-Mart's paint dept. the other day and did not find any mineral oil. I saw mineral spirits, and remembering there were several other names for mineral oil, I took a closer look. The label had all kinds of warnings about wearing rubber gloves and respirators, etc., and I slowly reached the conclusion that, "This is almost certainly not the main ingredient in baby oil!" :o)

 

So I went over to the pharmacy dept. and picked up a bottle of baby oil, with an ingredients list as follows: "mineral oil, parfum". Turned out to be just enough in the bottle to cover the rubber mini. Add another $3.50 or so to my bill for this thing - glad the original toy only cost $1! Hopefully the perfume won't interfere with the leaching of plasticizers and its smell will wash off fairly easily - baby-perfume smelling monsters with flakey paint jobs are not quite what I had in mind for this thing...

 

If I get any noticeable results from the oil-dip, I'll post them here in case the info is useful for those who might try converting/painting rubber toys in the future. It will have to soak for a few days though, and I'll be off-line for a few more after that. So hopefully nobody's holding their breath waiting except me.

 

Thanks for the tips & your interest,

 

Kang

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Sorry I missed this a few days ago. I had been busy with a few other things - so I was only able to check intermittently for additional questions.

 

The mineral oil/baby oil will work just fine. That is what I used during some of my first experiments with the bendy plastics. You can normally get larger containers of pure mineral oil from stores that sell mainly to farms. They use it for a variety of different things. Still, since the perfumed variety doesn't really cost much at all - there is no problem getting it at the local grocery store.

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Thanks again Joe, and no worries about the timing - that's one less potential pitfall I have to worry about so I'm a happy camper for the moment... Now I guess I just have to wait and see if it works on this kind of rubber!

 

Oh, and just in case anyone really is keeping an eye on this topic with a rubber toy in one hand and a bucket of mineral oil in the other (now there's an image...), you'll be happier than I was to learn I've had to postpone my upcoming cottage trip - so I shouldn't be off-line for as long as I had thought in my last post.

 

Kang

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