Airbrush primer woes

[Skerr]

Hi all,

 

I had a frustrating night last night attempting to prime Vallejo white surface primer on some plastic and resin model parts.

 

I used about 12 to 15 drops with 2 to 3 drops of thinner. no flow improver though.

 

I am painting at 17 to 20 psi with an Iwata hp cs eclipse. I am using the optional .50mm nozzle and needle for the first time rather than the stockk .35mm nozzle and needle.

 

the first few parts were no problem though as i needed more primer is when I had issues. splattering or misting, constantly cleaning the tip. My technique probably needs work as it tends to look, perhaps i keep the gun in one spot to long or totally misjudged where the paint will land.

 

I cleaned the gun 2 to 3 times though had to stop when the spring for the trigger went down the drain. A new one is arriving on Tues so I will give it another go though I am finding airbrush priming more difficult than airbrush painting. Same with varnish.

 

I am thinking i need to put less primer in the bowl to keep a ring from drying and causing clogs and increasing my ratio of thinner and using flow improver. Also being more mindful of sweeping my hand and not leaving it too long in place to pool. I was priming 5 infantry but they were all umassembled and mounted on wire and wine corks. Is that too much to airbrush in one sitting?

 

I think my psi is about right though will take any help I can get. Almost wants to make me go back to rattle can do to lost time but the airbrush results are so smooth.

 

What am I missing?

Edited March 4, 2018 by Skerr

[Bung]

You can go up with the psi. I normaly work with 25+ psi and a smaller nozzle.

I dont add any thinner to airbrushprimer and have no problems doing alot of miniatures.

I had the same problem with my first airbrush experience and what helped me was practising trigger control and working in thinner layers.

First if you release the airbrush trigger cut the paint but keep the air flowing.

 

The other point is work in thin layers, even if you spray 3 thin layers of primer to cover one spot you wont cover any details.

[Arkhanist]

Primer does cling on when it dries, more than standard acrylic - that's the idea anyway. 

 

This also means it sticks inside the airbrush easier. Vallejo primer does seem particularly prone to it though. Thinning is mainly to get it liquid enough for your nozzle size, so if it's flows fine when the brush is clean, it's thin enough. Vallejo primer should be thin enough with a .35 or 0.5mm.

 

There are a few things you can try. Higher pressure - I go to 25 to 30 for priming -  will get it through the brush quicker, and can help with minor clogging. Trigger control is important - if you let off the air before or at the same time as the paint, you get a blob of paint still in the nozzle - which either splatters when you next spray, or dries and clogs. So always cut to just air for a second before stopping spraying (i.e. forward, then up, not forward and up at the same time). If you're having significant paint dry around the cup, you have too much in for how quickly you're spraying. Use a smaller cup or just less paint and refill more often (or use a drying retarder, which I'll get to in a minute)

 

"I cleaned the gun 2 to 3 times though had to stop when the spring for the trigger went down the drain"

 

You shouldn't need to clean the brush under the tap for a flush. When you've emptied the cup of paint, fill it up with water and spray it into a waste pot to get out any liquid paint. Then a half cup or more of cleaner, and spray that into a waste pot. Then a final flush with water again, and maybe a quick wipe round the cup. You only need to clear the paint path - the cup, the two holes at the bottom where the needle comes in and out, the nozzle, and the front part of the needle. You can get the front tip of the needle and inside the nozzle with a q-tip soaked in cleaner and work the needle back and forth. The rest should clear with flushing with decent cleaner.

 

I use nail polish remover as a cleaner which is mostly acetone to flush between cups and final clean - it cuts through dry acrylic really well, but it can damage non-PTFE seals. I think the CS eclipse needle packing seal (between trigger and paint cup internally) isn't PTFE as standard, but you can get an upgrade to make it fully solvent proof. (cheap chinese ones and some starter brushes such as the iwata neo have rubber seals which is definitely vulnerable)

 

Disassembling partly when you're finished, to fully clean the needle and clean inside the paint flow path with soft brushes (I mostly use disposable inter-dental brushes and qtips soaked in cleaner). You shouldn't need to remove the rear spring or trigger assembly at all except if it falls out when you take the needle out.

 

If there's any paint in the trigger assembly area, you have a problem with the needle seal between the trigger area and the paint cup that stops paint flowing back along the needle and into the rear of the brush. Either tighten it or replace it, usually with a specialist screwdriver. For a deep clean every few sessions, I put all parts of the brush that come into contact with paint into a sonic cleaner with water and brush detergent, including the main body minus the air valve assembly.

 

If you're still having problems, then next thing to do is keep the paint liquid longer. Flow improver does retard drying somewhat and also makes paint spray more smoothly. I use a drop or two or vallejo airbrush flow improver with most every paint now, it does break down surface tension. I don't have to have it, but it does reduce tip dry nicely. (i.e. dry paint on the needle tip, which is a standard problem with acrylics). The extreme measure is adding a little slow dry, also called drying retarder, which will drastically increase paint liquid life. It can cause problems with adhesion though, so don't use it heavily.

 

One thing I don't do, but some do is to strain paint, i.e. run it through a fine mesh rather than neat into the brush. It would catch clumps in the bottle, but I haven't found it made enough difference to be worth the effort.

 

I did switch to badger stynylrez primer instead of vallejo, mainly as I was having issues with vallejo primer taking ages to fully cure and not sanding well. As a side effect, I've found I have less clogging/tip dry than vallejo primer (even with the above tips, I'd still have a clog sometimes with an extended session), so that's another thing that might help.

Edited March 5, 2018 by Arkhanist