Sunday, 20 January 2013

Hobby: Spraying models on a cold day

Recently I have had a chance to finish some miniatures and put them up on the blog (see 'Completed' above). I'm never one to tread carefully around them from then on though, with many a miniature getting chipped in transport and through general wargaming use. I've actually been clumsy enough to drop someone else's models at a tournament once (which shattering as it toppled off the table), and spent the rest of the game having my models moved for me as I was politely asked to take a step back from the table.

With this in mind I always try to apply a protective clear coat or varnish to models once they are completed.

The Horror Story:

The models on the centre and right have been sprayed using a matte clear finish, which cause 'ghosting'.

When I first moved to Canada from Australia I had little knowledge of spraying in cold environments and proceeded as usual: cardboard box on a chair, spray the models, leave the can outside while they dry, come back 10 minutes later and spray the other side. Only problem was, I came back only to find severe 'ghosting' had occurred as the clear coat dried, which proceeded to worsen as each coat was applied.

I took the (what I assumed to be faulty) can back to the store with the models and was able to get a refund and a few tips as well as a change of brand, but since then I have always been careful to follow a few simple rules to prevent having to repaint anything in the future!

My initial solution was to apply a clear coat with a brush, preventing any possible spray problems. I have had great success with Games Workshop's Clear Varnish (now renamed 'Ard Coat), and I even use it to seal sections of a model as I finish painting them, to prevent damage to the completed areas.

The reds have been clear coated on the centre model to protect them while I painted the metal areas.

This was all well and good, but shiny models tend to look like they have been 'dipped' to create the shading, and look less 'grim dark' (The Warhammer 40,000 style) and more G.I. Joe. The solution for me has lay partly in the choice of product, and in the method of spraying.

The same model when finished, with the addition of a matte clear coat.

The Solution:

Firstly, it is good to know how the white 'ghosting' occurs. As I understand it, the pressurised propellant and paint mixture rapidly drops in temperature as it exits the nozzle, picking up some of the ambient air in the process. If any part of this mixture (most likely any water in the air) freezes before it reaches the model, the paint does not dry or adhere evenly, and instead forms patches across the surface of the model, causing the 'ghosting' as above.

What causes this to happen? Low Temperatures and High Humidity.

You want to make sure the can is as warm as possible before spraying. The models are outside because of the fumes!

Having switched to Testor's Dullcoat (now labelled as a generic 'Spray Lacquer' with a frosted lid to denote the matte clear coat) I have had zero problems when spraying with a well shaken can, which remains inside at a temperature of 25 degrees celsius (77 F), even between coats. The models can stay outside in low temperatures, I have sprayed right down to 2 degrees celsius (35 F) with no problems. Once the warm paint mixture has reached them the cold temperatures serve only to slow the drying process. Patience is the key for multiple coats! Please note, I have done no high humidity testing, 40k and tropical holidays with your significant other don't tend to work well together!

Always remember the basics when using a spray can, you want light even coats at an equal distance.
Never start or stop spraying at a model. 
The current Testors packaging.

1 comment:

  1. After undergoing this exact same debacle (I've done this before too, but after a year or two, I end up repeating my mistakes anyway), I think I'm going to try and find a matt sealer that I can airbrush on. Perhaps airbrushing indoors at room temperature might just be the ticket on a cold humid day. It's certainly worked for primer so far (Vallejo makes a decent airbrush-able primer).