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Spraying a couple of things with Citadel Chaos Black tonight, and I noticed on the second coat, that some areas were taking on a subtle rippled texture. Is this because the temperature is dropping or because I didn't wait long enough between coats?

It could be not allowing time for the previous coat to dry. I could be too much paint, too close it's the can, not shaken enough (inconsistent pressure) or a blocked nozzle.. Any number of things including the weather.

The important thing is to not feel discouraged. Test it out again after a good shake and wipe down the nozzle, and see what it does to sprue or a plastic yoghurt tub under similar conditions.

You really only need one coating, and it should be a light one at that.

 troa wrote:
You really only need one coating, and it should be a light one at that.

I'm not sure how I could get complete coverage in one coat. You have to be able to get at it from underneath, but you don't want to touch the model while it's wet.


Automatically Appended Next Post:

 Buttery Commissar wrote:
It could be not allowing time for the previous coat to dry. I could be too much paint, too close it's the can, not shaken enough (inconsistent pressure) or a blocked nozzle.. Any number of things including the weather.

The important thing is to not feel discouraged. Test it out again after a good shake and wipe down the nozzle, and see what it does to sprue or a plastic yoghurt tub under similar conditions.

Upon closer inspection, it seems to be doing it in some of the places where it's thinnest, and one of the removable panels only got one coat a side, so I figure it must be the temp, or maybe it's that I didn't shake it enough (did for a good 30 seconds), or perhaps it's the pressure as the can is getting low?... Definitely wasn't too close.

I've sanded the spots inquestion, and I'll spray it again when the sun's out. I'm also going to try a trick I read about elsewhere, and run the can under a hot tap first. It's supposed to help the spray go on smooth. Warming the model is supposed to help as well, so i'm toying with the idea of giving it a couple min in the oven at 100 degrees first as well...

Get a wooden baton (1x2 or 2x2) and put a strip of double sided tape on it. You can then stick a lone of models to the tape and the ability to turn them every which way (including upside down) means that you can prime all of the nooks and crannies without multiple coats.

If you want full coverage you're always going to need several coats because you have to spray it from multiple angles to get the nooks and crannies which means the raised areas naturally get multiple layers.

I usually stick models to a sprue so then I can spray up from below to hit those areas.

Whether or not you actually need full coverage? If the reason you're spraying it black is simply so subsequent layers stick better, you don't really need full coverage. If you actually want the model to be black then obviously you want full coverage.

I can't say I've ever had rippling, my first bet would be applying the paint too thickly or too thickly over a semi-dry layer. But it's never happened to me so I dunno.

Warming the can raises the pressure so can give better results, especially in cold weather where a cold can means insufficient pressure, if you're spraying a lot the can will cool down as you go, so it can be useful having a bucket of warm water to put the can in periodically.

A warning about heating up the models themselves, polystyrene has a melting temperature of a bit over 200C, however the glass transition temp is around 100C and you can start losing details or damage the model very easily around that temperature.

Spraying from too close is usually the main cause of rippling, but if you kept a good distance and are seeing it in lighter coated areas, your models might not be clean. Dirt, finger oil, etc can cause primer to not stick properly. To avoid that, give everything a wash with lightly soapy water, rinse, and fully dry before priming. Handle them by the base after washing. Also when using spray primer, always keep the can moving while you spray.

I don't use GW primer so others might have suggestions about temperature etc. I actually use Rust-Oleum 2x Ultra Cover primer and it works great on metal or plastic (and is way cheaper). You do need to use it outside, but I just lay my models out on a large piece of paper, spray lightly from multiple angles, then flip and repeat after a couple hours when they're dry to the touch.

Also until you find a procedure you're happy with, just prime one model at a time.