I hear modelers say we should wash models to get rid of the "releasing agent" so the paint sticks to the plastic better.. My question is: is it enough to wash everything before building the kit when everything is still on the sprues? Or does the grease and dirt from our fingers while building the kit and handling the parts require another wash before painting? I was just thinking that very small parts, especially PE, will start falling off while washing?! Any tips or advice on this subject?

Thanks
Hisham

I occasionally soak a pre-painted piece in a tub of water and Windex. Rinse it off, let it air dry and begin painting.

I rinse everything in soapy water immediately before painting. I have heard many people say that it is unnecessary, but after spending perhaps 100 hours on a build why not spend an extra hour washing and drying to make sure there is no reason for the paint not to stick? The plastic always looks less shiny after washing, so there is definitely something coming off the surface...

I would say it's more critical if you're painting with acrylics, as they are more sensitive to oil or silicones. I've never had an adhesion problem when working with enamels.

Like Aaron, I wash my builds just before painting.

I use warm soapy water in the kitchen sink. I rinse under running warm water and wick the water off with paper towels and air dry. I use ordinary dish soap and a large, soft water color paint brush to agitate and scrub with. If possible, I immerse the entire subassembly in the soapy water and just "swish" it back and forth rather than scrub it. Sometimes though, scrubbing is needed.

I keep the sink plugged while washing and rinsing in case I break off a part (very rare). I take my time, don't get too aggressive with the brush, and only do one subassembly or part at a time (so I can keep track of parts and know to look for any that might break off or get dropped into the water).

I wash for two reasons:

It definitely improves paint adhesion - acrylics especially. Enamels and lacquers generally "bite" through any oils or finger prints on the plastic by virtue of their thinners/carriers.

However, even for enamels and lacquers, washing removes dust, sanding residue, sawing swarf, chips from carving and scraping, etc. There's more to getting model clean enough for the paint besides just oils and fingerprints.

Clean models make for neat painting. Also, if the model is clean, the need for special primers is mitigated or eliminated. Because I wash my models before I paint, I generally do not use any dedicated primers. Any primer painting I do is done just for the purposes of colors (undercoating, pre-shading, etc).

Finally, after I wash my models, I never touch the model with my bare hands again unless I thoroughly wash my hands before. It does no good to wash the model, and then get greasy finger prints all over it. Latex or cotton gloves are even better.

If you're careful, breaking parts off is not the risk that you might think. I very rarely do any damage during the washing stage.

Models can get very "dirty" during construction. Sanding, carving, scraping, drilling, sawing, and buffing with steel wool leave all sorts of stuff on and in the model. Sitting on your work bench for a few weeks (or months, in my case) allows dust to settle on the model and parts. So, it's not just the possibility of mold release oils and residue or finger prints that can ruin your paint job.