I have been trying, rather less than successfully, to spray some shells, one with Tamiya TS-16 and another with X8 Yellow.  I have applied three light coats to each shell and allowed to dry between each coat...the result for each is very thin and patchy coating and it looks quite horrible.

Over they years I have found that all yellows I try result in the same effect...it has to be me, but what am I doing wrong? In the case of the TS-16, there is no thinning, straight from the can after a solid 5 minutes shaking it

Doesn't explain the patchiness, but what did you prime it with, and what was the primer color?

I find yellows and reds work best over very light grey to even white primer.

Tamiya light grey primer, single coat

I've not sprayed much yellow paint, but a tip I was given for many spray paints is to sit the can for a time in a container of warm/hot water before use. The only other things I can think of is too humid or too hot.

I may strip the whole thing back and try again....soak in Isopropyl alcohol overnight, or is there a better way?

Hmmmm.... I'm wondering whether it is an air-brush/compressor issue?

What pressure are you spraying at? Is there any moisture in the air flow? can you adjust the spray pattern? perhaps try a smaller/narrow spray pattern. Maybe you need to use a lower pressure? Instead of spraying a model, get a sheet of styrene and try out a few of these variables see if that changes anything.

Back to paint... I note that you have shaken the paint. Have you actually tried stirring the paint? I have this mini power tool paint stirrer which mixes the paint far better than what shaking will do. Some yellows will get a solid particle layer that needs to get mixed in. What about trying a different brand of paint???

Everything else seems right. Grey primer is always what I recommend.

Hope this helps.

Hmmmm.... I'm wondering whether it is an air-brush/compressor issue?

What pressure are you spraying at? Is there any moisture in the air flow? can you adjust the spray pattern? perhaps try a smaller/narrow spray pattern. Maybe you need to use a lower pressure? Instead of spraying a model, get a sheet of styrene and tray out a few of these variables see if that changes anything.

Back to paint... I note that you have shaken the paint. Have you actually tried stirring the paint? I have this mini power tool paint stirrer which mixes the paint far better than what shaking will do. Some yellows will get a solid particle layer that needs to get mixed in. What about trying a different brand of paint???

Everything else seems right. Grey primer is always what I recommend.

Hope this helps.

Gremlin wrote in the original post: there is no thinning, straight from the can after a solid 5 minutes shaking it

Am I correct in thinking that he/you are using an aerosol can....not an airbrush?

Back in the days when I was building/painting kits for a second income, I had a useful little gadget inside my paint booth. It comprised of a small electric (12v) motor from something like an old cassette player, with an extended shaft made from a piece of square brass tubing. That extension was about 60mm long and in the end of it I cut a thin gap and inserted a piece of scrap brass from a etch sheet (DJH models); soldered in place...about 3mm x 10mm.

I connected the wires for the motor to my good ol' H&M duette and place the jar of paint up so the "stirrer" was at the bottom of the jar. Hold the jar with one hand and operate the H&M with the other.....result was a proper-good mixed-up paint bottle.

Another idea I have employed over the years is to open a new tin of paint and drop-in a small nut or ball bearing, seal the tin up again and shake the bottle/can. The new foreign object does the job of mixing-in the solid stuff.

Personally, I wouldn't even consider using an aerosol can to spray a model. Just my choice though.

Roachie

TS paints are 'Tamiya Spray' ie aerosol.

The X are bottled paints.

So...any suggestions for the best way to strip everything back and start again...soak overnight in isopropyl alcohol or coke or...?

So...any suggestions for the best way to strip everything back and start again...soak overnight in isopropyl alcohol or coke or...?

Depends if it is plastic, metal or some other material.

If isopropyl alcohol thins the paint then I'd give that a go as the stripper. I would also be reasonably surprised if IPA hurt the plastic, but that said, go for a gentle wipe with a cotton bud or piece of sponge type foam.

Plastic from, Phil Badger and Peter Boorman...so possibly castings...

Okay, so if you're talking about polyurethane then the news is a little worse.

Avoid prolonged exposure to IPA.

(I can be properly nerdy on this topic)

Earlier in the year I ran data and numerical analysis on a question very similar to this for a friend of mine looking to patent a new recipe of aliphatic polycarbonate polyurethane. Intended for use in the medical field, the primary property of interest looked at was it's ability to withstand exposure to oxidising and reducing agents, saline solutions and EtOH.

We were time exposure testing the urethane in >70% solution EtOH and IPA at up to 37C temperatures, the good news is his new polymer was pretty good, the bad news is the general samples it tested against were not that good. (Read up on ethanol locks for sterilisation of catheters as to why this data was important).

I no longer have the data, but I do recall that some polyurethanes were distorted dimensionally, and in cross-sectional shape, and also often in colour against the control after as little as 10 minute exposure times.

As an aside, whilst peforming this testing, it was decided that it should be tested against domestic, household methylated spirit (in case in home use someone got desperate and used their on hand alcohol for the sanitisation). I was of course being very careful measuring and weighing my solvents and reagents, and I am not a chemist, but I couldn't work out why some of the measurements I was taking did not correspond to my calculations, so I was thinking about the denaturing compound throwing me off.

Anyway, long story short, I eventually discovered my source of discrepancy, it turns out that household 'metho' is now actually 'etho' - reading the bottle (always the last resort as we know) your common, garden variety 'methylated spirit' is now denatured ethanol...

Then you probably don't want to soak it in IPA.   Windex with ammonia is also quite good at removing Tamiya paints (but eats glue joints, especially CA/Super Glue) if you haven't clear coated it.

Both work even better if you can scuff the surface of the paint a little with a stiff bristled brush.

An alternative is to not strip it and just re-prime.  You mentioned that the yellow has gone on very thin; if it's not filling in fine details perhaps just work on top of it?