AndersP Posted April 30, 2016 Posted April 30, 2016 (edited) Hi guys, I've recently returned to modelling and now have a sizeable stash of kits to work my way through, but I've hit a rather annoying stumbling block on my first go. I decided to start with a Tamiya Mini Cooper 1:24 scale, and wanted to paint this up in the same colour as my first car. After a few goes at mixing up by eye, using Tamiya Acrylics, I stumbled across the Revell Aqua Color No.30 – Orange, as it’s exactly what I need. So, I duly washed all plastic parts and primed them up using Humbrol 24 – Trainer Matt Yellow, thinned with Humbrol Enamel thinners through my airbrush. After applying three coats and leaving 24hrs in between each, I then left the model for a week. Next I applied a couple of coats of the Revell Aqua Color orange, laying the second down nice and wet so as to get a gloss finish, which it did. After leaving the car for another week, I decided to apply a light coat of Humbrol Clear Gloss Varnish, which sprayed straight out of the bottle and went on very nicely. After a few hours I went over again with the Humbrol Clear Gloss Varnish and got a lovely high gloss finish from it that still looked wet even when it had dried for an hour or so. The model was then put into a Tupperware type box with the lid only partially on, so that any fumes could evaporate and dust would be kept to a minimum. I left it in there for a few days and when I returned I was horrified to see that the roof had a heavy crazing effect that resembled the surface of an easter egg, and that the rest of the model was covered in very fine crazing, although for some reason the front wings were less affected, despite these being given a more liberal application of paint and varnish than the rest of the model. That was four weeks ago. Today I decided that I would strip all of the paint off and start from scratch, but before I do I decided to give the micromesh that I’d got recently a go. I chose the roof as this would be easiest to do as a quick test, and I also wanted to only do half of the roof so that I could see the before and after effects. The micromesh did a fairly decent job but the crazing was too deep to remove so I abandoned it. However, when I put the piece down I could see that where my thumb had been gripping the part, that the paint surface had moved and also that my thumbprints were everywhere. I thought that this stuff was supposed to dry tough(?). My hands had been clean when I started and I hadn’t touched any chemicals, so I’m at a loss as to why the surface should be pliable. Could somebody please suggest what I may have done wrong, or whether this is a common problem using this type of product? My thumb doesn’t have any colour transfer, so I’m assuming that it’s literally just the top coat of Humbrol Clear Gloss Varnish that is the problem. I’ve attached/linked a few photos below showing the awful roof bonnet, but the almost unaffected front wings and offside. Do all gloss coats have the potential to do this? If not, then could someone also please suggest a decent alternative that allows a high gloss shine to be had off the gun, rather than just through polishing, or should I just go out and buy some automotive 2 pac lacquer and hardener, like the stuff I used to use years ago as a car painter? Also, in terms of stripping this model back to bare plastic – is toilet bleach a suitable medium? Thanks in advance, Anders Edited April 30, 2016 by AndersP
PhantomBigStu Posted April 30, 2016 Posted April 30, 2016 Mixing enamels and acrylics is the problem, can paint enamels over acrylics, but the other way round ends in what you've described
WildWeasel Posted April 30, 2016 Posted April 30, 2016 Humbrol gloss is awful, I had exactly the same issue with crazy paving. I stripped my model down using Gunze Aqueous thinners rubbed on with kitchen roll. I now use Gunze Aqueous for clear coats. I've tried Johnsons Klear as well but found it a little too runny.
AndersP Posted April 30, 2016 Author Posted April 30, 2016 Thanks PhantomBigStu - I also have a Tamiya Honda CB750F that I've already primed using the same enamel yellow, and was going to spray with Tamiya acrylics, so now I can avoid making the same mistake twice! WildWeasel - did you experience the crazing with the Humbrol Gloss after using enamels too, or does this stuff just craze no matter where it's used?
WildWeasel Posted April 30, 2016 Posted April 30, 2016 I had laid it over Gunze Aqueous Acylics, I would only use it over Humbrol Acrylics (which are also awful, so its gone in the bin!)
AndersP Posted May 1, 2016 Author Posted May 1, 2016 Thanks. Has anybody used the Humbrol Clear Gloss Varnish over Tamiya Acrylics with any degree of success, or should I literally just bin the two bottles that I have? WildWeasel - The Gunze stuff doesn't look easy to come by (I don't use the bay after being ripped off massively years ago), but I can get my hands on some Alclad Clear fairly easily. Is the Alclad prone to crazing when used over Tamiya Acrylics too, or is it a completely different story?
dubster72 Posted May 1, 2016 Posted May 1, 2016 There's absolutely no question that this should not have happened. A water soluble acrylic coat is generally unlikely to interact with the paint beneath it, especially when it's been left to cure for that amount of time. I use Humbrol Clear as my go-to gloss varnish; over Tamiya acrylics, Humbrol enamels, Vallejo Model Air. I've never had this problem. In fact, I'm inclined to think that it's down to some weird delayed reaction between the two paint types, rather than the clear coat. No scientific reason, just my gut feeling! Stu's comment re acrylics over enamels is incorrect I'm afraid. There's more potential for problems going the other way around, because oil based products are chemically hotter than acrylic ones. Obviously there is a possibility that you've got a dud bottle of Clear. You could always email Humbrol & ask for a refund. Personally, I'd try using it again over paint from a single manufacturer and see what the result is. 1
lesliegl Posted May 2, 2016 Posted May 2, 2016 My experience since buying a bottle is to use it on a model which had been airbrushed with Mr Hobby acrylic..Revell Aqua and Tamiya acrylic with no problems...takes a while to dry but when it does it gives a great gloss finish.. I've also hand brushed a couple of coats onto a Hellcat drop tank I'd painted with Humbrol acrylic Sky 90 and got a rich deep gloss as good as I've ever seen on here.. Leslie
AndersP Posted May 3, 2016 Author Posted May 3, 2016 Thanks guys. I've actually stripped back the mini using Mr Muscle and it's come up virtually brand new. However, I'd also painted up a Tamiya motorcycle seat, using the same primer but this time I used Tamiya acrylic paint (black rubber) as a base coat, and then gave a couple of light coats with the Humbrol Clear Gloss Varnish. There was no crazing or softening of the paint surface. After soaking both of them in MM and then running under the hot tap, the Revell Aqua Color orange came of in stringy latex like chunks, whilst the Tamiya Acrylic just turned the water black and didn't seem to release any chunks of paint. I wonder if the issue was with the Revell Aqua Color (possibly because it was a gloss), or whether the issue didn't happen to the Tamiya because it was a matt finish(?).
Sprtt Posted January 23, 2021 Posted January 23, 2021 I’ve found that the rattle can Humbrol Enamel Gloss Varnish can be workable. A couple key things to remember is hold it very far away from your model and a little goes a looooong way! It’ll yellow and crack if you put on too heavy a coating. Also you can get bubbles on the finish if your spray coat is too heavy. Getting the can to spray can be a challenge but warm ambient temperature and a lot of agitation prior to starting helps.
treker_ed Posted January 23, 2021 Posted January 23, 2021 I use the Humbrol clear over Tamiya X & XF paints as well, and never had those sort of problems. Have also used it over Humbrol, K-Colour metallic, Vallejo acrylic metallic, and Xtracrylic paints. Don't use Revell Aqua anymore due to the very limited colour pallet that they have, and insisting on mixing colours and not giving the correct names, eg Insignia blue or Camouflage Grey or Sky, and only giving their own paint colours for anything! At least Humbrol or Tamiya try to get the names right most of the time!
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