Washing Kits with detergent

[echen]

At what point should kit parts be washed with detergent to remove moulding chemicals?

On the sprues? Off the sprues but before construction? After construction? Before painting? Between coats?

I'd be interested in what the experienced experts advise. I've been building kits for years and, lately, had issues with paint adherence. In days of yore I just used to slap some Humbrol enamel on and they looked fine but more recently both enamel and acrylics insist on being patchy until several coats have built up and obscured at least some of the detail.

Please help. 😖

Edited December 29, 2021 by echen
clarification

[Stef N.]

I'd give them a once over while on the sprue and then maybe once assembled/in sub assemblies if you have handled the parts a lot without gloves. I do the second part more often.

[echen]

Thanks Stef. I know I should have known this years ago but better late than never! 😀

[dogsbody]

On my last build, I forgot to wash the sprues before I began assembly. So I just continued building and just prior to painting, I wiped the surfaces down with a round makeup pad that was dampened with 99% Iso-alcohol. That seemed to work pretty good.

 

 

Chris

[echen]

Thanks Mate. Worth knowing.👍

[Bertie McBoatface]

 Unless I spot that brown waxy residue in the corners during the first examination of my parts, I tend not to bother. I generally use a brilliant primer called StyNylRez from Badger and that seems to stick to just about everything.

 

For the interiors of aircraft and tanks, I don't even prime anymore since I discovered Tamiya lacquer thinners, they seem to burn into the plastic and stick really well.

 

For exteriors, if I can see greasy fingerprints, I wipe down with Isopropyl Alcohol. I have never done this on a tank though because the surfaces are so complicated, I suppose.

 

 

[echen]

Cheers Bertie. Would this work with a hairy stick as opposed to an airbrush?

[dnl42]

I like to use isopropyl alcohol to wipe down all parts just prior to painting.

[Bertie McBoatface]

13 minutes ago, echen said:

Cheers Bertie. Would this work with a hairy stick as opposed to an airbrush?

 

I can't say. My first coat in any circumstances is always sprayed. I would never brush paint on bare plastic no matter how clean it was.

 

(By the way, because you didn't quote me or use my @Bertie Psmith, I wouldn't normally have seen your reply and question. It was just luck that I saw it on the View New Content tab.)

[Ade H]

What would anyone be trying to wash off before construction?

 

The silicone-free release agent which may be impregnated into modern polystyrene compounds? Because I'm confident that it's paintable (it's described so) and not removable, fairly obviously. Separate release agent should be obvious if you ever encounter it; but I wonder who's even using it now? I've never seen it on PS moldings, although I don't have any kits from the previous century... Granted, some plastics may feel a little bit weird and slippery despite no release agent residue (HobbyBoss, I'm looking at you) but washing doesn't improve that (I tried).

 

Any concerns about grease and dust can be addressed as other respondents have suggested, or by using vinyl gloves or tips and a dusting brush.

 

But in any case, the whole question of whether it matters can be answered, at least on a case by case basis, by testing with an unwanted part or a runner. Testing avoids a lot of problems.

 

(By the way, I keep notifications off and rely on watching threads because of the excessive quoting. Too 'noisy' otherwise.)

[dogsbody]

I've got an Eastern European kit of a Tu-2 that feels like it has a coating of cosmoline smeared all over it. If I ever build it, it will require some strong industrial cleaner to get that crap cleaned off.

 

 

 

Chris

[dnl42]

1 minute ago, dogsbody said:

I've got an Eastern European kit of a Tu-2 that feels like it has a coating of cosmoline smeared all over it. If I ever build it, it will require some strong industrial cleaner to get that crap cleaned off.

I've had a couple of resin kits like this. What a mess! 😱

[echen]

3 hours ago, Bertie Psmith said:

(By the way, because you didn't quote me or use my @Bertie Psmith, I wouldn't normally have seen your reply and question. It was just luck that I saw it on the View New Content tab.)

Thanks for the advice on correspondence - I wasn't aware of the @Bertie Psmith convention here.

[Bertie McBoatface]

I received that one !  🙂

[ckw]

17 hours ago, echen said:

In days of yore I just used to slap some Humbrol enamel on and they looked fine but more recently both enamel and acrylics insist on being patchy until several coats have built up and obscured at least some of the detail.

I don't see that washing the sprues can do any harm, but for me a wipe down with IPA or Mr Hobby thinners just before painting is more important so as to remove any finger grease, marker residue (I use markers to check for good seams) etc.

 

If you are still using Humbrol paints, that may be the problem. There seems little doubt that the quality and consistency of Humbrol paints has suffered in recent years.

 

Cheers

 

Colin

[Alan P]

This has been interesting to read. I generally wash down the main assembly of an aircraft just before the primer goes on to remove fingerprints, dust, static and sanding residue. Never really considered moulding release agent as an issue for injection kits .

 

In any case, I never considered IPA as a pre-paint treatment, I'm sure it's a faster solution. As a pretty lazy modeller, anything that offers a shortcut is good news 😂

[malpaso]

I always wash the sprues before I start.  I’m not sure it’s needed nowadays but it’s kind of a zen thing to open up the kit, contemplate and examine the sprues and get clues how well it’s made.

 

On the other hand I don’t get problems with masking tape ripping off earlier layers of paint so maybe there’s something in the idea.

[spruecutter96]

To be honest, I get the impression that mould-release agent could be a thing of the past. I would say that modern mould-production is generally so precise and fine-engineered that it has removed the need for a "lubricant" to help ease the parts out of the mould. I think the technology has made the need for the agent recede.

 

This is just an educated-guess, admittedly. 

 

Chris. 

[Pin]

I never do

[JohnT]

Oddly I don’t recall a paint problem in the  60’s, 70’s and 80’s with brush hairy stick painting using then decent Humbrol paints straight onto bare plastic without primer. 
 

What happened to improve things? 

[Ade H]

I don’t get problems with masking tape ripping off paint either, even though as I hinted, I never wash (...the kit, I mean...) before construction because there should be nothing to remove from a modern molding.

 

I wonder whether this old habit will soon fade away out of practicality in line with the increased occurence of small and delicate parts, because there's no way that I'd wash a modern AFV kit's runners, even if I thought that there was any point.