Tiny White Spots using Vallejo Semi-mat Varnish

[Guest]

I have sprayed (by AB) the underside of the wings and the fuselage with Vallejo semi-mat varnish, thoroughly shaken with a rattle nut. Room temperature for everything (varnish, thinner, AB and the model parts). There are many tiny white spots on the parts, smaller than a pinhead. I diluted with about 10% Vallejo thinner, 18 PSI, sprayed just to wetness to achieve cover. The spots appeared immediately I started spraying.

When I used Tamiya matt varnish on my 1/72 Spit I got white colouring collecting in the panel lines here and there. I understand that matt and semi-matt varnishes contain a white powder which prevents a shiny skin forming.

Once thoroughly hardened (24 hours) I will consider using a micromash cloth to remove the spots and re-spray.

But what caused the spots, and what would be the best way to remove them, and to prevent them re-appearing when re-spraying?

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[Guest]

Steve I had bottle of varnish (semi matt do you mean satin ?) think it was matt which was part of a defective batch.

Email Vallejo giving the symptoms but also the batch number on the capsule.Think it is the number under the data code. But I would also give the data coding as well. They will tell you I am sure what is wrong & if it is a poor batch.

Laurie

[Guest]

Steve I had bottle of varnish (semi matt do you mean satin ?) think it was matt which was part of a defective batch.Email Vallejo giving the symptoms but also the batch number on the capsule.Think it is the number under the data code. But I would also give the data coding as well. They will tell you I am sure what is wrong & if it is a poor batch.

Laurie

Thanks. I will do that.

[ojays]

A question,

(1 )If you look very closely at the spots, do the resemble a little crater? (hard edges with a lip)

The reason I ask is if they do, the problem could be minute droplets of moisture/water coming through the airline and atomising with the air/paint mixture. As the paint cures, the moisture bubble bursts often leaving a minute white crater.

(2) Do you use an in line water/moisture trap?

If the answer to the question (1) is yes, and question (2) no, this could be what is happening.

Moisture often builds up inside the air reservoir and releases into the out going air, a moisture trap does as it says!

Just an idea from past experience in the paint-shop!

Gregg

[Guest]

Gregg:

No crater. The spots are round with no surface feature. I have been working on the problem and found that with very fine micromesh I could remove nearly all the spots. I also found that by very carefully using the point of my Xacto craft knife I could flick the larger spots away. They were separate objects. Peculiar! It implies that the spots were separate objects which landed on the wet varnish on the model. That would then imply that the white powder was not properly mixed (despite very thorough shaking with a rattle nut inside). I have sent a message to Vallejo giving the symptoms and the batch number, as Laurie sugested.

On moisture/water, I have a compressor with a tank and a trap.

I will need to repaint affected areas then revarnish when I demonstrate that the varnish I use is trouble-free. I might instead test and use Tamiya semi-mat. Fortunately, being cautious, I varnished only the black underside of the Lancaster, so respraying will not be as difficult as if the problem areas involved the upper side camo.

[Guest]

its not residue from off the mixing nut that has worked loose is it?

Just a thought as they use a cooling compound during manufacture, one of the reasons ball bearings are really the better option in my opinion.

[BarryW]

Steve I often get that and it infuriated me at first. I think these are small flecks in the air that settle on the model, possibly coming from kitchen paper used in a/b clean-ups.

Now, no worries, after a lot of experiment I found an easy way to deal with them. After at least 24 hours drying time for the varnish to harden rub the specks down, lightly, with a fine sanding stick (micromesh should do).. Don't be too heavy handed and you will not notice that you did this after but it works....

[Guest]

Yes Barry that brings up a number of problems using kitchen roll. Some of them are terrible & those with a coloured pattern release the colour. Best I have found is the jumbo roll that £1 shop markets.

Nice thing about Harder & Steinbeck is that the paint cup is removable & so easy to rinse of any paper rubbish. On my new Iwata I have found it best to remove the needle nozzle for a good flow of water thro while cleaning the integral cup to avoid these bits. First time I used it I personally learnt this advice after getting a fragment of paper stuck. Please note this is not a go at either types of airbrush only advice on how to go about cleaning.

Laurie

[Guest]

its not residue from off the mixing nut that has worked loose is it?Just a thought as they use a cooling compound during manufacture, one of the reasons ball bearings are really the better option in my opinion.

I don't think so. All the spots are perfect circles.

I assume that ball bearings might be better because they don't have threads in which flakes can settle. But since Vallejo bottles have a spout, wouldn't a ball bearing, being spherical, block the nozzle? What is your experience of that?

[Guest]

Steve I often get that and it infuriated me at first. I think these are small flecks in the air that settle on the model, possibly coming from kitchen paper used in a/b clean-ups.Now, no worries, after a lot of experiment I found an easy way to deal with them. After at least 24 hours drying time for the varnish to harden rub the specks down, lightly, with a fine sanding stick (micromesh should do).. Don't be too heavy handed and you will not notice that you did this after but it works....

I have had some success rubbing with micromesh. It's worrying that you have had the same fault.

[stona]

I think those spots are something to do with the matting agent, though Gregg (ojays) made a very valid point about moisture above too. If you are sure that you had thoroughly mixed the varnish and then mixed it again (a rule I use for my enamel paints too) I'd chuck the bottle and start a new one.

Here's my quick wash with an Iwata.

1/2cup of cleaner (white spirit in my case) and squirt it though, including a bit of a back flush. Wipe with kitchen roll

1/2 cup of cleaner, loosen and remove needle with cleaner in bowl, squirt most of it through including a back flush. Wipe bowl again.

Clean and replace needle. 1/2 cup of cleaner and spray through working needle back and forth.

Sometimes I might repeat the second step if I can still see some colour in the flush.

That's it. It takes about two minutes and it's all I ever do to my airbrush(es) unless something goes wrong, which is very rare, or I decide to give them all a bit of tlc and a thorough clean, which is equally rare.

If you've followed my builds here I can tell you that the last time I completely stripped and cleaned my main airbrush was before I started my Hawker Tempest.

For a thorough clean I disassemble the brush and clean everything with cellulose thinners, inter dental brushes etc, before giving the parts a spin in an ultrasound cleaner. If something hasn't been quite right I examine the needle and nozzle parts under a magnifier and replace if damaged. I then put everything back together and lubricate with WD 40.......that's right WD 40.

I also occasionally lubricate the trigger mechanism and spray a little WD 40 through the brush during general use. I follow it with 1/2 cup of solvent. It's a tip I got from a professional airbrush artist and It's never caused me any problems despite howls of protest from some in the modelling fraternity

Cheers

Steve

[Guest]

Just had a look at my Vallejo Varnishes. Opened each one up gloss matt satin. Dipped a paint stirrer to the bottom & the consistency is the same through out. Just need a gentle roll to make sure & mix the small drop of thinners collected at the top.

Same for most of the Model Air. You do not need the ball bearing etc just the gentle roll. They are consistent from top to bottom. The ones that need a good stir are those which have a residue of left behind pigments at the very top of the bottle. I have found, from experiment, that it is not a good idea to shake as it results in some paint spurting into the lid & around the top of the nozzle which causes no end of trouble. I roll (recommended by Vallejo to stop bubbles forming) & use a mechanical vibrator mixer. For the pigment left at the top types I open up & gently stir.

For Model I always, now, open up & stir gently. They are mostly thick at the bottom.

Thanks for the Iwata clean info. Steve. Just got a conversion Triple Action Handle. This, they say, gives quick needle release quick flush & a preset on the handle. Not used it yet. But will sitrep findings.

Laurie

[Guest]

It was just a thought that crossed my mind that may have been overlooked, just thinking outside the box as it were with a view to hopefully helping.

Vallejo bottles have a spout, wouldn't a ball bearing, being spherical, block the nozzle? What is your experience of that?

I have non in this instance, I don't use an airbrush for modeling but have used one for artistry.

All the times I've come across needing to add a mixing item it has been bearings, they are round so there's no sharp edges or corners to damage the inside of the pot and maybe chip off some of the plastic inside and introduce a "blocking particle" to the paint.

Also there's no threads where substances can coagulate and then be deposited back in the paint after they've possibly hardened.

Most of the cans/tubs//pots of paint I used bearings with were metal and nuts would have dented the metal with a vigorous shake thinking about it

Hope you find what caused this soon and can get back to spraying with no worries.

[Dave W]

This problem is one I have had many times over the years.I used to get it whenever I used Humbrol matt clear enamel.When I tried Vallejo it worked perfectly,and I thought I had found the perfect matt varnish.But I've had the white patch problem on two models recently.Dont know if it's to do with a defective batch,but I threw the bottle away the first time it happened and bought another.Used on my last build and got white patches again.Going to try another make next

[Guest]

I think those spots are something to do with the matting agent, though…….

Your routine is interesting. I do part of it every time I finish an AB session! Because of very frustrating blockages when I started airbrushing in February I have always soaked the loose parts in AB cleaner, then cleaned, with a tiny bottle brush and AB cleaner, the nozzle (using an interdental brush for that) and its cap, the passage between the front and the cup, the cup, and the needle, then I put it all in an ultrasonic cleaner. As a result the only blockage I have had was due to a paint (Vallejo acrylic) which had a strong tendency to clump in the bottle and my strong shaking was not enough.

However, that seems to be obsessive, particularly given your simple method for routine cleaning, which I will use in future.