Friday, 11 May 2018

Star Wars AT-ST [WIP - Phase Two of the Hull, Drive Engine & Gyro System; Oil Dot Filter Weathering]

As a work-in-progress update it's pretty hard to distinguish between Phase One and Phase Two of the weathering process. Firstly there the technical issue with photography which I'll get into in more detail later. And secondly there's the slightly overenthusiastic way I had approached Phase One which resulted in certain sections having a more pronounced rust stains than I had originally wanted. This had an undesired effect of rendering subsequent layers oil dot filter weathering to become almost imperceptible. But thankfully this only occurred in areas of the AT-ST with too much rust stains. 

Chromatic variation is most apparent in the AT-ST's gyro system ...
... but on the walker's side panels the rust stains seem to have overwhelmed all other filtered hues

Materials used for this weathering technique comprised oil paints from two brands namely Winsor & Newton and Abteilung 502 as well as Artists' White Spirit from the former. Differences between oil paints from the two brands, at least from what I've observed when working with them, is as follows:

   (a) It has been said that being Winsor & Newton's mid-range offering, the Winton oil colors have a lower pigment load/density compared with Abteilung 502 oils which were specially formulated for modelers. This seemed to be the case as the latter had better surface adhesion and didn't wash away so readily when blended with white spirit. In terms of pigment load/density, Abteilung 502 oils are allegedly closer to Winsor & Newton's premium range i.e. Artists' Oil Colour.
   (b) There was far less linseed oil medium in the Abteilung 502 oil paints compared with the Winton oil colors. As such, the former doesn't have to be placed as long on the cardboard palette during the linseed oil leaching process. This particular property could also have contributed to (a) above in that the Abteilung 502 oil paint dried out more making it harder to blend into a filter. It's just an educated guess mind you as I didn't set up any control experiments.     

Winsor & Newton Winton and Abteilung 502 oil paints were used for the oil dot filter weathering technique 
Linseed oil inside the paints was leached out onto a cardboard palette ...
... overnight in an enclosed plastic container
Oil paints had a more matt look to them the next day

After the oil dot filter weathering process, I had applied another protective clear coat for subsequent weathering steps. And here I caught a lucky break for, you see, I had sprayed on a lacquer clear coat over the oil paints. Technically this is a no-no because the solvent inherent in a lacquer paints can potentially dissolve the oil paints and cause a horrible mess. But none of this happened. My guess is that three factors had come into play: (1) Sufficient time was allowed for the oil paints to dry and cure; (2) Being applied as a filter meant low amounts of oil paint was left on the surface, which incidentally allowed them to dry faster too; and (3) In relatively hot weather, a significant amount of solvent had evaporated when the lacquer clear coat was sprayed onto the surface area.  

A clear lacquer coat was used to seal in the oil dot filter effects (see post for caveats to this step)

That being said it is still advisable to use acrylic clear coats as the preferred method of protecting an underlying oil-based layer. In cases whereby a substantial amount of oil paints have been used in the previous step (e.g. using oil paints to paint skin tone) it would be suicidal to believe the underlying layer of oil paints won't be affected in any way by a lacquer coat on top of it. Results of the oil dot filter weathering process on surface areas basecoated in light grey can be seen in the photos below. 

Most recognizable piece of hull of the AT-ST, it being the front-end and all
Closeup of the front-end of the hull better reveals the chromatic variations
A clearer view of the chromatic variations introduced by the oil dot filter technique

Compared to what can be seen with the naked eye, the resulting chromatic variations achieved using the oil dot filter weathering technique become relatively poor visuals when viewed through these photos. This is largely caused by my struggle to obtain an optimal level of white balance during the photography session. White balance is a critical component of photography that can affect how the hues look like in the display screen of a viewer's electronic device. Moreover white balance is especially vital when dealing with predominantly monotone hues, which is the case for the AT-ST.    

Look closely enough and you'll see hints of blue green/white/grey/blue mixed in with the rust stains
It's almost imperceptible but the monotone light grey hues is now more varied chromatically
AT-ST side panels with the rust stains and oil dot filter weathering

One key thing I noticed was a slightly greenish tint in the photos that became very pronounced on certain brands of electrical devices. To counter this I tried to adjust the white balance of the final photos by using the plain manila Microsoft Picture Manager. So all I could effectively do was try to fix the greenish tint by adjusting the overall colors towards the magenta spectrum. It's extremely frustrating when you realize that it's mostly out of your hands how observers view your photos, color-wise. Because I cannot possibly account for every type of display in the market I tend to concentrate on making the colors looks as accurate as possible only on Windows and Apple devices.

Yet another section in which I might've overdone the rust stain weathering
Ditto for the underside of this section because the rust hues have overwhelmed the other colors
Although other filter hues are present, one tends to notice the bluish green tints more as they complement the rust hues
I'm thinking of either leaving the flexible steel pipes nonmetallic or just drybrush a light coating of metallics   
Gyro system of the AT-ST after being weathered with rust stains and oil dot filters
Even the command viewport hatches and smaller side panels are not spared from oil dot filter weathering

Phase Three of the weathering process is coming up and it's one in which the changes in between phases are drastic enough to be easily noticeable. This phase, which involves painting micro paint chips, is a tricky and time consuming process. But once it's done, the level of realism on the AT-ST walker should ratchet up exponentially. That's something to look forward to after a fairly boring transition from Phase One to Phase Two. Thanks for reading this post anyway though!


  1. Your eye for detail is astonishing.
    That already looks wonderful.

  2. Looks fantastic ! I'm looking forward to the next step !

  3. Another masterclass in preparation and detailing.

  4. Fabulous. I do enjoy seeing these different techniques.

  5. The amount of love you are putting into this is wonderful an certainly pays off. The results may not be that visible at the first moment, but once you put everything together the overall impression is incredibly natural. wonderful.

    1. Thank you for the vote of confidence Suber! :)
      That's the bane of work-in-progress blog posts. Sometimes they can be very boring. But then again sometimes it can be of help to some modelers. I'm hoping it's the latter for the most part.

  6. While not being overly visible on the first look I feel filtering does really make an otherwise plane looking piece look interesting. Never thought about storing oil paints in a wet palette, but I might try that next time.

    1. Ohhh sorry if my post above wasn't clear but the oil paints were NOT stored in a wet palette. All I did was place them on a cardboard inside a plastic container so that the linseed oil could leach out overnight without the paint drying too much.

    2. Thanks for the clarification. When reading your text again I‘ve to admit it’s probably been more a case of not reading thoroughly the first time.


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