Varnishing with airbrush issues-help-Updated

[Defiant911]

I’m a newbie to the modelling.
I have a dual action airbrush which I have been using for the first time to spray paint my models. Painting has gone very well and the finish has been great but whenever I airbrush the varnish (humbrol clear gloss varnish) I keep getting a very mottled and patchy finish which frankly looks awful. I’m spraying at around 18psi pressure from and inch or two distance away from the model. I have attacked a picture showing the type of poor finish I’m getting. Can anyone offer any tips how to correct my mistake please.
carl

 

[Archetype]

Did you clean the surface prior to varnishing? Looks to me like the surface was greasy prior to application.

 

[Defiant911]

Did you clean the surface prior to varnishing? Looks to me like the surface was greasy prior to application.

I have done the weathering and then wanted to seal it all in. I thought it was ok to spray a varnish layer after weathering? Is theee anything I can do to repair the finish? Thanks in advance.

 

[Archetype]

Yep, you should have been. The only other ting I would be worried about is whether any thinning agents were used that could have affected it.

I can't think of anything mechanical that would have caused that, so I'm at the limit of my experience there I'm afraid.

Hope you suss it out.

 

[Archetype]

Just thinking....what are the weathering products you used? Are they oil based, or oil paints?

 

[rtfoe]

Carl, clearly there is a reaction from the previous paint or weathering material with the varnish. Can you list the types of paints used as whether they are oil or water-based including the varnish plus the length of time in between application?

Cheers,
Richard

 

[Defiant911]

I sprayed a thin coat of varnish after competing the painting in acrylic reveal paints. I used the ak panel liners (Ak2070) which I think are oil based. Given that I have sprayed the model Initially with acrylic paints would this be an issue I hadn’t considered. My in experience thought these were ok to use over acrylic paints? Should I be using something else to weather my models?

 

[Defiant911]

Carl, clearly there is a reaction from the previous paint or weathering material with the varnish. Can you list the types of paints used as whether they are oil or water-based including the varnish plus the length of time in between application?

Cheers,
Richard

As mentioned, revel aqua paints and ak weathering. Using the humbrol clear gloss varnish. Quite a combination

 

[Archetype]

Oil on water based would be fine. Not the other way round.

 

[Defiant911]

As mentioned, revel aqua paints and ak weathering. Using the humbrol clear gloss varnish. Quite a combination

Oh, I left the Modelmover night from the AK weathering before applying the gloss varnish so about 14 hours ?

 

[rtfoe]

Is the Humbrol clear varnish oil based or waterbased?

 

[Defiant911]

Another picture although I’m not sure how clear this has come out

 

[rtfoe]

With all that weathering can't see the varnish effect except it could look like morning dew on the tanks surface.

Cheers,
Richard

 

[Defiant911]

With all that weathering can't see the varnish effect except it could look like morning dew on the tanks surface.

Cheers,
Richard

It certainly looks a bit like dew although that was not my intended effect. Out of curiosity what is your general application when applying varnish, e,g, psi from compressor, distance from model with airbrush and general motion applying it? Just wondering if it’s part to do with my setup and application. As I say, this is only my third model sim I’m very much learning from my mistakes.

 

[Jack L]

In my experience, gloss varnish does tend to 'pool into globules' slightly...and you have to apply a bit more than you feel is fight to get an even finish. I might be doing something quite wrong, but have only had one issue of spraying too much, where it ran off. Matt varnish (for me) reacts very differently and I spray pretty sparingly.

PSI, I just guess until the flow looks right, as with the distance from model, depending on the surface area, but I would say 3-4 inches away. I use a slow sweeping method back and forth, starting and finishing away from the model.

 

[Defiant911]

In my experience, gloss varnish does tend to 'pool into globules' slightly...and you have to apply a bit more than you feel is fight to get an even finish. I might be doing something quite wrong, but have only had one issue of spraying too much, where it ran off. Matt varnish (for me) reacts very differently and I spray pretty sparingly.

PSI, I just guess until the flow looks right, as with the distance from model, depending on the surface area, but I would say 3-4 inches away. I use a slow sweeping method back and forth, starting and finishing away from the model.

Thanks Jack, maybe that’s the key, to spray more to fill the voids as it were. What pressure do you use to spray at. There seems to be a fine line with not enough pressure and the spray pattern becomes less consistent to too much pressure and blasting the model. I have been experimenting but as a rule of thumb found my self setting the psi between 15-20 psi but too be honest this seems to be subjective. Carl

 

[Jim R]

Hi Carl
It does indeed look as if the varnish has pooled on the surface - I imagine a water based varnish on a slightly oily/greasy surface. My thoughts would be .....
Try adding a drop of washing up liquid to the varnish to break the surface tension. This will only help if the varnish is water based. If the varnish is solvent based you'll just get a gloopy mess.
Try spraying a very light, mist coat of varnish and let it dry thoroughly before spraying the actual gloss coat.
Make certain the paint/weathering is totally dry. Leave at least 48 hours in a warm place before varnishing.

Just a few thoughts which may help.
Jim

 

[JR]

Carl.
Just reading what Jim has said sounds about right to me. I'd spray in very thin coats, letting each one dry, and increase the pressure to 20 psi.
The second photo by the way is great, nice weathering and not over done.

 

[Deleted member 7181]

I agree with the above too, the varnish really didn't want to be on that surface so it's pooled up. Maybe the AK stuff hadn't thoroughly dried, or handling the model to apply it has left greasy finger prints on the surface.

Try spraying a very light, mist coat of varnish and let it dry thoroughly before spraying the actual gloss coat.

This would be my approach, and the one I use all the time in my day job as well. What we call "grip & rip" or the Yanks call "tack & whack". The light initial gives the wet coat something to grip to so it's much less likely to separate or pool up.

 

[Defiant911]

Thanks all for the great advice. I have an almost finished Messerschmitt to weather and gloss shortly so I will take this approach and hopefully achieve a better finish. The last time I made a model was about 34 years ago and there’s a lot more products on the market these days. It’s quite difficult to know what’s best. However with an abundance of YouTube tutorials and the help of this forum I hope to improve with each model and let’s face it, like most of us I’m going to have plenty of free time indoors at the moment.