Friday, July 8, 2011

Tutorial: "Polishing" Metal Models for Painting

It took me several years to pick this little trick up and, since then, I haven't finished one miniature without using either one or both of these methods.

The issue I always had was that my paint would never really "flow" well over the miniature. It was very prevalent whenever I'd use a wash and the wash would seem to "settle" throughout the area, instead of seeping into recesses and leaving high areas without shading. This was always a side effect of the metal miniature underneath.

The cause is partially a factor of the metal itself but also an aftereffect of the casting process. Both of these things together cause the miniature's surface to develop very tiny ridges and valleys, giving the surface a "Flat" or "Matte" appearance or finish. I discussed finishes in more detail in the Paint 101 Tutorial for those interested but it's enough to say here that whatever else is put over this finish - primer, paint, washes, etc - takes on the same or similar properties.

While a nice, low profile Matte finish provides a good foundation (or "ground") for paint adhesion; a severe Matte finish can cause paint to flow incorrectly, to take on a Matte finish when one is not wanted (as in the case of Gloss finishes), and/or for the bumps in the metal to become evident in the final piece. "Polishing" attempts to solve this somewhat. The methods below are an attempt to grind or sand the metal surface into a Semi-Gloss finish - just enough to provide a good ground for paint adhesion, but not severe enough to affect paint flow and properties.

FYI, re: Greenstuff and "Polishing": Always be sure to polish your mini before attempting any greenstuff work or sculpting. The instructions below only work on white metal/lead surfaces and will damage any delicate greenstuff work.


Method 1: Steel Wool + Time = Polished Mini!

This is a good method for highly detailed minis where a Dremel could easily destroy detail or for those of you who don't own a Dremel (note: WTH is wrong with you!? Go buy a Dremel, it saves tons of time!).

What you'll need:

  • A white metal (pewter, lead, tin, etc.) miniature
  • Fine Steel Wool
  • (Optional - for sanding out "micro-pitting") Jeweler's files and/or sandpaper
Step 1

Once the miniature is ready for polishing, rinse it well under cool water to remove any excess dirt, dust, or metal shavings. Any of these can scour or scratch the surface of the mini where you don't want it.

For this tutorial, I'm using Reaper Chronoscope's Natalya. This is a slim, well-detailed mini that could easily be damaged by using a rotary tool to polish. It's pictured above, totally unpolished...

Step 2

Some minis have been incorrectly cooled following casting and suffer from "micro-pitting". These are tiny pits in the metal surface and must be sanded or filed away before polishing. This can be done with either jeweler's files or sandpaper. If the pitting is too deep or filing would destroy detail, you can skip this step for now and fill the pits with Green-stuff after polishing.

Remember, if you use sandpaper to remove "micro-pitting", to rinse the mini before continuing on.

Step 3

Using the steel wool, begin "sanding" the surface of the miniature all-round. I find it helpful to start from the top and work down the miniature. Try to focus on large flat areas for now. If you're worried about destroying raised details, use soft indirect pressure and "polish" in a circle motion.

Compared to the last picture, I've begun polishing from Natalya's head downward to her waist. It's a little hard to tell from the pic but you may notice the mini's surface is smoother and shinier.


Once you've given it a good once-over....

Step 4

You should notice the mini is noticeably more shiny, especially in large flat areas and raised parts. The mini still may have some areas you were unable to reach into, like between collars and shirts, under slung weapons, and inside coats or other outerwear. Now, focus on those areas.

Break off small bits of steel wool and try to fit them into the gaps and crevices, sanding with medium pressure, in any direction possible.

Below the mini has been fully polished. Compare this to the 1st pic, especially in the thigh area in the foreground, and you'll easily spot the difference. This largely smooth surface is much easier to paint than the rough, matte surface the mini originally had.


A super-polished, glossy surface isn't necessary and, in the case of small miniatures devoted to gaming, is not advised. A super-polished surface provides little to no paint adhesion and is really only good for large display miniatures.

Step 5

When you're comfortable with the finish, stop and fully wash the mini with warm water and dish soap. Rinse well under warm water and let it fully dry before priming (or adding Greenstuff details).


Method 2: Dremel + a Delicate Tough = Polished Mini...in less time

A quicker method that takes a little practice but can save time.

What you'll need:
  • A white metal (pewter, lead, tin, etc.) miniature
  • Water
  • Dremel or other Multitool (I use a Dremel Stylus)
  • Brass Wire Brush (Dremel #530)
  • Carbon Steel Wire Brush (Dremel #428) or Stainless Steel Wire Brush (Dremel #535)
  • (Optional - for small spots) Cylindrical Wire Brush (Dremel #443)
  • (Optional - for "super polishing") Nylon Bristle Brush (Dremel #404)
  • (Optional - for grinding out "micro-pitting"/cracks) High Speed Cutters (Dremel #125, etc.)
A note on safety: Whenever using ANY of the above brushes or tools, ALWAYS wear some form of eye protection, no matter how low your RPMs are set! It's common for wire brushes to "shed" a bristle now and then and it's easier to scoop them into the trash or pluck them out of your skin, than out of your eye.

Bristle Brush Stiffness

From my experience, here's a list of the the bristle brushes from above, graded from most to least stiff:

  • Carbon-Steel: VERY stiff, recommended for low to no lead content miniatures only
  • Stainless Steel: Stiff, a good all-round bristle for all but the softest metals
  • Brass: Somewhat stiff, good for detailing
  • Nylon: Hardly stiff at all, ideal for super polishing (if you're so inclined)
In reality, the only two brushes you truly need for this process of Stainless Steel and Brass. I've included the others here for those who are so inclined to use them.


Step 1

Once the miniature is ready for polishing, rinse it well under cool water to remove any excess dirt, dust, or metal shavings. Any of these can scour or scratch the surface of the mini where you don't want it.

Step 2

Some minis have been incorrectly cooled following casting and suffer from "micro-pitting". These are tiny pits in the metal surface and must be sanded or filed away before polishing. This can be done with either jeweler's files or sandpaper. If the pitting is too deep or filing would destroy detail, you can skip this step for now and fill the pits with Green-stuff after polishing.

Alternatively, you can attempt to grind the surface of the miniature down around the pitted around by using a High-Speed Cutter. This should ONLY be attempted on areas that lack highly-detailed surrounding surfaces. It is ideally suited for pitted areas that lack detail, such as billowing capes, rumpled clothing, etc.

For this I recommend either a Dremel #192, 117, or 125:















Begin by setting your multitool ~10K RPM (Speed 3-4 on the Dremel) and carving around the pitted area, attempting to blend it into the surrounding area. You may have to set your speed higher or lower depending upon the depth and width of the pitted area.

Don't try to get it entirely perfect with the high-speed cutter. It's impossible really, as the cutter isn't designed for really smooth, delicate work. Instead, switch to either a Carbon-Steel or Stainless-Steel bristle brush, working from the outer edges of the affected area inwards. This provides a smooth transition between the non-affected areas surrounding the cuts.


Note: Some of you may be asking "why not just use the bristle brush to dig out the pitting?"...Well, I've tried this and it will ruin a perfectly good bristle brush in no time. A bristle brush tool isn't designed to handle the pressure and intense heat that digging out the pitting requires. This is why you start with a heavy-duty tool bit and work downwards to more delicate bits, both in this step and throughout the entire process.

Remember, if you use sandpaper or a Multitool to remove "micro-pitting", to rinse the mini before continuing on.

Step 3

Using the your Carbon-Steel or Stainless-Steel bristle brush, begin lightly polishing the surface of the miniature all-round. I find it helpful to start from the top and work down the miniature. Try to focus on large flat areas for now.

Start around 7,500 RPM (Speed 2 on the Dremel) and use light pressure, just ever so slightly hitting the surface of the miniature. Don't attempt to apply heavy pressure. Instead, if you find the surface difficult to polish, increase the speed to ~10K RPM (Speed 3-4), use a moderate pressure, and try to make multiple passes around the miniature.

Increasing the pressure significantly will have two negative effects. First, you can easily ruin raised details in a matter of seconds. Second, and most importantly, you will begin building up heat within the metal. The problem with heating the metal like this is, as it is focused in one area, the metal will heat (and cool) unevenly, weakening delicate parts. Additionally, heat will begin to build with the bristle brush, shortening its life and making it easier for individual bristles to "shed" while the tool is going at speed, which can lead to injury.

The main purpose of this step is to polish out bad areas (see Step 2) and to give the miniature, as a whole, a good even polish, NOT to make it super-shiny or to focus on individual parts. For this, we go to....

Step 4

You should notice the mini is noticeably more shiny, especially in large flat areas and raised parts. The mini still may have some areas you were unable to reach into, like between collars and shirts, under slung weapons, and inside coats or other outerwear. Now, focus on those areas.

Using the Brass wire brush on a higher speed, attempt to get into recessed areas being sure not to apply too much pressure and always checking the area after a few passes. This is the step where I try to move the miniature into different positions to get a smooth, even polish.

Step 5

If you're really, super inclined to get a great finish, put your multitool aside for now and use the steel wool process above. At most gaming scales (6-32mm), this step isn't needed and will generally be more work then its worth.

Step 6

If you're satisfied with the finish at this point, wash your miniature with soapy water to remove any excess metal dust or bits, dry for a couple of hours, and either continue unto the next step for super-polishing or prime and paint...

Step 7

Super-polishing really isn't necessary and can sometimes provide a surface too-smooth for good paint adhesion. I honestly don't recommend this for any miniature you plan on handling and/or throwing in a storage case for any amount of time. On 54mm or larger scale miniatures meant for display, this step may come in handy. As always, YMMV...

Using a Nylon bristle brush on ~12-15K RPMs (Speeds 5-7), begin by working over the surface of the miniature applying light pressure and making passing in a circular motion. You're attempting to get a highly polished surface and it may take some time and a lot of patience to achieve. As above, try to avoid building up excessive heat and/or pressure.


2 comments:

Felix said...

"Jeremy?! What are you doing in there? You stop whatever it is and come out this instant."

"But honey, I'm polishing my..."

"That's it! You're opening this door right now!"

Tony said...

Interesting article.

I tend to brush my minis with an old toothbrush or a green pot scourer (Scotchbrite) rather than using wire wool.

I brush the mini under warm water and can use either dishwashing soap or even cream cleaner.

I also clean the mini with the same brush and washing up liquid after adding either Milliput or Green Stuff.

I hope this helps.

Tony
http://dampfpanzerwagon.blogspot.com/