Changing Paint consistency

[Jack L]

Does/Can paint consistency change mid use? Been painting the cremeweiss on the interior as show (Mig Ammo paint + vallejo thinner + vallejo flow improver, no idea what ratio), and for the majority, the paint was perfect. A really nice consistency, then suddenly the adherence to the primer became non existent.

Any suggestions as to why? It's quite warm in my office, so is an element of it evaporating as I'm painting? I'm not a big fan of Mig paints, but as I have the colours. This happened twice, I remixed and fixed it after the first time, and then it happened again a few minutes later. You can see at the top of the photo compared to the rest. primed with Tamiya Extra Fine Primer, and left for 24 hours before second coat.

 

[Dave Ward]

Jack,
that's certainly very odd - is there any chance the paint/thinners/flow improver separating?, or not mixing completely? Any chance of the primer being contaminated in a certain area? It's probably just a fad of mine, but I don't like mixing different makers' paint/thinners, there's always a chance that they're not compatible
Dave

 

[Jack L]

Jack,
that's certainly very odd - is there any chance the paint/thinners/flow improver separating?, or not mixing completely? Any chance of the primer being contaminated in a certain area? It's probably just a fad of mine, but I don't like mixing different makers' paint/thinners, there's always a chance that they're not compatible
Dave

That's all I can think of Dave, that it's separating mid use, or similar. I'm confident it's well mixed when I start. I don't think an issue with the primer...spraying on some scrap gave me this same issue.
No I normally don't mix brands...but I'm stubborn and refuse to throw away these mig paints. They are supposed to be ready to use but far from it. But not had this issue before after initially getting the mix right.

 

[yak face]

I agree with dave , it sounds ( and looks ) to me like the mix is seperating out mid use . Ive had paints do this to me before , maybe it could be something to do with the pigment? . If its fairly dense and heavy then after the initial mixing it could be slowly sinking and seperating . Also try a mix without the flow improver to see if thats the issue ? Cheers tony

 

[Tim Marlow]

Hi Jack
Are you sure this isn’t a fingerprint from the build? Did you wash the kit before painting? It could be that the fingerprint grease migrated through the primer as it dried (being soluble in Tamiya primer) and resided on the surface? Water based acrylic hates oil and grease.

 

[Jack L]

I agree with dave , it sounds ( and looks ) to me like the mix is seperating out mid use . Ive had paints do this to me before , maybe it could be something to do with the pigment? . If its fairly dense and heavy then after the initial mixing it could be slowly sinking and seperating . Also try a mix without the flow improver to see if thats the issue ? Cheers tony

I'll try and identify what's doing it on some scrap. The flow improver was really doing the trick to get this paint useable, so I hope it's not that!!

 

[Jack L]

Hi Jack
Are you sure this isn’t a fingerprint from the build? Did you wash the kit before painting? It could be that the fingerprint grease migrated through the primer as it dried (being soluble in Tamiya primer) and resided on the surface? Water based acrylic hates oil and grease.

I can't be certain, but I don't think so. I always spray on some scrap or paper first to test the paint, and it was fine...then when this happened, I re-sprayed the scrap and got the same effect. So I'm fairly sure it's the paint and not the surface. However, I didn't wash it, and rarely do, unless the plastic appears particularly greasy.

 

[Ian M]

I have a suspicion that it's the mix of mig and Vallejo

 

[stona]

I'm tending towards Tim's suspicions in post #5.

It looks like something has worked its way through or found its way onto the primer and is interfering with the adherence of the paint. A really bad case of 'fish eyes'.

 

[JR]

I'm with Steve and Tim .
I used Mig, along with Vallejo thinners and flow improved. Add too much flow improver and you get a blotchy finish, but that looks more like underlying grease .

 

[Jack L]

Thanks all for the replies. Learnings for the future. Thankfully the affected area will be completely out of sight, so it's no drama. Just one for me to watch for ahead.

 

[Deleted member 7181]

I'd agree with those that think it's surface contamination. The two fish eyes on the panel top right of that picture are classic examples.

If you want to have a go at covering the area, just for testing for future occasions, my best advice is to dust a couple of very very light coats over it first, drying in between. Coats so light that it looks like you've put nothing on.

Doing that, the paint film is so thin that it can't flow anywhere so won't separate over the contamination, but will leave just enough on the surface for the wetter layers that follow to cling onto without spreading (in my trade we call them grip / gripper coats)

Adhesion won't be as good over the area, but it's a good save for problem sections like that.

 

[David Lovell]

I'd have thought that if the surface was that contaminated the primer would not have adhered to it , Tamiya extra fine used it once drys extremely smooth and so hard almost verges on brittle I had no problem with covering it but adhesion was very poor it had to be handled with kid gloves.
No idea what ratio? Not my go to brand but I do use them and would take Mig over Vallejo every day of the week ,I'd have thought acrylic thinner was pretty universal but saying that I've never used theirs nor migs. I don't know how you mix your paint but try starting 60 paint 40 thinner if still heavy thin even more I often work 50 50 or or more on the thinner side ,why flow improver surely that's what the thinners is for ditch it .I only mix in the air brush cup keeping tabs on what I'm doing makes it easy to mix the same again if I run out. What air pressure are you using almost looks like you've gone in to close with the airbrush trying to get around the nooks and crannies, good luck with this problem please don't let it beat you we've all suffered setbacks in this hobby where things haven't gone the way we wanted ,im sure that this causes that lack of mojo thing stick with it and please let us know the outcome. Dave

 

[Tim Marlow]

Not the case with organic solvent based primers Dave. The solvent dissolves contaminating finger oils and greases, but still allows the primer to adhere.

I’ve had exactly the same issue with Tamiya extra fine white though. It was like brush painting on dusted chalk! Took me ages to work out where all the white particles were coming from! The grey normal primer is fantastic though, sticks really well....

I decant it into a glass bottle, allow the propellant to gas off, then dilute about fifty fifty with MLT to spray.

 

[David Lovell]

Not the case with organic solvent based primers Dave. The solvent dissolves contaminating finger oils and greases, but still allows the primer to adhere.

I’ve had exactly the same issue with Tamiya extra fine white though. It was like brush painting on dusted chalk! Took me ages to work out where all the white particles were coming from! The grey normal primer is fantastic though, sticks really well....

I decant it into a glass bottle, allow the propellant to gas off, then dilute about fifty fifty with MLT to spray.

Morning Tim must admit that when it comes to primer now ,this sounds like bit of a back pedal I only use black or grey mig one shot the bottles say no need to thin but I take it down to 50 50 or more then two or three light coats without stopping works for me so its one of thoes if it ain't broke things. All my acrylic paints I thin with mr color aqueous thinner all my lacquer paint (mr hobby)I thin with mr color thinner and mr hobby self leveling both of wich insedently thin tamiya acrylic superbly. Iknow it seems ive got a pet hate for Vallejo but model air doesn't spray from the bottle as claimed they sell you thinners and here's the big heads up flow improver? . The only paint that I've used that spluttered and spat plus produced that strange phenomenon drying on your tip was Vallejo best move i ever made was to bin it but then this hobby is a one man learning curve you can watch the vids read the books ask and listen as much as you like you have to find your own happy medium from these. Like I said I hope Jack gets sorted when these things happen it is a set back to your confidence wich I think is a large part of this hobby. Dave

 

[Tim Marlow]

Hi mate
Agree ref spraying Vallejo (or any water based acrylic). Simply awful for me. I tried several times and gave it up as a bad job and went back to Tamiya.
My regime these days is lacquer primer, Tamiya or Mr Color spray coats, and Vallejo brush paint. Flow improver is really a brush painting tool that can be used for making washes and glazes.
The confidence issue is a problem. The only way to deal with it is put the issue in perspective. It’s only plastic and paint. Nobody dies and nobody else is affected. If something bad happens, take a deep breath, swear a bit, then try something else. If that doesn't work either, swear again and try a third option. If all fails, throw it in the bin and open another box. In the long term you will grow as a modeller because failure and success, through experimentation, are really the only way you learn.

 

[Jack L]

Thanks all for the input. Thankfully nothing ruined, the area will be out of sight, and I can go back to my trusted MRP and Mr Leveling Thinner for the rest of the build, but notes taken for the next time the MIG comes out.