Varnish questions

[Gern]

Hi guys. Some serious help needed her please.

My grandson PJ and I are both working on an aircraft build. PJ has the Tamiya Spitfire Vb and I have the Tamiya Rufe floatplane.

Base colour has been applied to both. PJ used an A/B with a mix of Tamiya colours while mine was painted with a hairy stick using lots of thin coats of Model Air. That was last week.

On Monday we decided to varnish using a hairy stick as we both need the practice. We put on two coats of Klear with about an hour's drying time, then two coats of Humbrol Gloss - again with about an hour drying time between coats.

PJ's kit has ended up with, at best, a sort of satin appearance, while mine is really shiny but about as smooth as a pebble beach! Like so:





We both used a similar flat brush about 1 cm wide and we both shared the same containers of varnish - undiluted Klear from an old empty paint jar and undiluted Humbrol straight from the bottle.

Where are we going wrong?

[Tim Marlow]

Not sure to be honest Dave, but the effect you’ve got on the Rufe happened to me on a canopy once, and is why I no longer dip canopies in Klear.

[stillp]

I don't think an hour's drying is enough Dave. No idea why the two models came out differently though.
Pete

[Tim Marlow]

I don't think an hour's drying is enough Dave. No idea why the two models came out differently though.
Pete

Good point Pete. The satin effect could then be achieved because a sprayed matt finish is always more pronounced than a brush painted one. If the matt was more pronounced the overlaying gloss may not then smooth out the surface enough to generate a high gloss.

[Gern]

Thanks guys. Now I don't know whether to try and correct the finishes we have, or strip them off back to plastic and start again. If I decide to strip them, any suggestions as to what to use? Bearing in mind I can't just soak them or we'll lose all our cockpit paint.

Tim: Your comment reminds me I had a similar problem with a canopy some years ago. It's possible I may have a bottle of Klear which has somehow gone off or got polluted with something. I'm going to replace it and see if that works better.

As far as the sprayed surface being less smooth than the brush painted one, I must admit that it does feel rougher. I'm sure I've read that it may be caused by the paint starting to dry before it has time to level out properly. I also read on here recently that the warm weather can add to the problem. I can't do anything about that as PJ is only here during the daytime so spraying in the cooler evenings is not an option. Would a higher/lower A/B pressure help or should I spray closer?

[Gern]

I don't think an hour's drying is enough Dave. No idea why the two models came out differently though.
Pete

You could be right Pete, although Humbrol says 30 minutes between coats and Klear is supposed to be dry in 20 minutes. Either way, a longer drying time won't do any harm.

[Tim Marlow]

I would go with spraying closer Dave, but remember, matt paint is always rougher. That’s why it’s matt. The rough surface scatters the light rather than reflecting it.

[stillp]

Thanks guys. Now I don't know whether to try and correct the finishes we have, or strip them off back to plastic and start again. If I decide to strip them, any suggestions as to what to use? Bearing in mind I can't just soak them or we'll lose all our cockpit paint.

I've stripped parts of a plane by using IPA on a tissue, with a cotton bud for the awkward bits.
Pete

[Gern]

I would go with spraying closer Dave, but remember, matt paint is always rougher. That’s why it’s matt. The rough surface scatters the light rather than reflecting it.

Looks like I got some experimenting to do. There has to be a way or no-one would use Tamiya matt acrylics.

[Jim R]

I also read on here recently that the warm weather can add to the problem.

When the weather is very warm I only airbrush early morning or late evening. Although I have no proof of a connection between high temperature and poor paint finish it makes sense and on a couple of occasions when the paint has gone on badly it was very warm in the work room.

[Gern]

I've started stripping my Rufe. So far I've tried IPA and Methylated Spirits using an old toothbrush. Both are working but the meths seems a little quicker - although there's not a lot of difference. I've dumped my old bottle of Klear and I'll stick with the Humbrol gloss when I come to varnish again. Fingers crossed.

[Scratchbuilder]

If that is the floor polish Klear then you will get problems brushing as the liquid will dry at differing times, far easier to spray even with a cheap Badger 250. Far better to use something like Humbrol gloss for brushing.

[Gern]

If that is the floor polish Klear then you will get problems brushing as the liquid will dry at differing times, far easier to spray even with a cheap Badger 250. Far better to use something like Humbrol gloss for brushing.

Would it help the drying time and levelling if I diluted it with water? That's if I can find some. My local Tesco doesn't have ANY liquid polish - only aerosol spray cans and those squeegee type spray bottles.

[yak face]

You say you put on two coats of Klear with an hour in between dave? That could be the start of the problem - klear will dissolve itself so the second coat will have softened and lifted the first. I usually only give one coat or if I need a second I’ll give it at least 24 hours to harden . Second are you using the new Humbrol Clear ? If so then its a different animal altogether from the johnsons Klear . The Humbrol is quite a bit more solvent based and will attack paint if not fully cured . I got a bottle to try and didnt like it at all. Maybe the combination of the Klear softening the first coat and then the two coats if Humbrol doing the same gave the patchy results? Add into this the very warm weather and its no surprise . Heres what works for me - after painting and leaving to cure 24 hrs I give it one brushed coat of Klear . This is left another 24 hours then I decal . I dont use any decal softener or fixer , all I do is paint a small area of Klear where the decal is to go. This helps to eliminate silvering and as it dries the decal will conform to any surface detail ,raised or recessed .A few times I have tried decal softener (gunze mr softer) but found it doesnt work any better than my method so only use it in extreme cases , plus it can react with the Klear and leave a mark. Good luck with the second try , cheers tony

[rtfoe]

Tony has hit it on the nail with his explanation.

Cheers,
Richard