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Cutting/Painting plastic advice

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  • Member since
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Cutting/Painting plastic advice
Posted by Traincraft199 on Monday, March 29, 2021 3:08 PM

I have an unassembled atlas 721 building I want to modify. I want to cut 2 large windows in the front like this:

and I want to paint the building a more dull shade of brick color. But I have some questions:

1. What's the best way of cutting plastic cleanly without damaging it?

2. What type of paint should I use that won't cover up the molded brick details?

edit: the plastic I need to cut is about 1.5 millimeters thick

 

I'm going for the look of this building: https://www.google.com/maps/@40.1583009,-76.3073692,3a,48.7y,307.74h,99.91t/data=!3m6!1e1!3m4!1sztooXMR0ElFqjhpfv4LWFw!2e0!7i16384!8i8192

Building my first layout, 4x8 contemporary urban area in HO scale 

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Posted by mbinsewi on Monday, March 29, 2021 3:49 PM

A supply of #11 blades for your hobby/Exacto knive, layout the window opening, follow horizontal brick joints, and scribe away.

For the vertical cuts, also follow brick joints,  using a straight edge, as you'll be cutting a vertical joint, then the next course, you'll be cutting a brick in half, etc, etc.

When your done, for the vertical cut, you could take your knive blade and cut a return at the horizontal joints, to make it look like a half brick, if you follow what I trying to describe.

As far as the color, you'll have to match the photo to the paint of your choice.

Use flat paint, or use a Dullcoat finish when your done.  

I take the paint out of spray cans, and use with my air brush.  Right from the can, it's usually ready for an air brush, although when using primers, you might have to thin a little.

Mike.

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Posted by MisterBeasley on Monday, March 29, 2021 4:34 PM

I use rust or rust-brown rattle can primer straight from the can for brick buildings.  It works well.

I would get a piece of Walthers brick sheet and compare the brick size and appearance to the building you have.  Then I'd cut the bottom story off and create a new one with the brick sheet.  This avoids making awkward inside corner cuts.

Another tool that might be useful is a razor saw.

It takes an iron man to play with a toy iron horse. 

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Posted by hornblower on Monday, March 29, 2021 4:43 PM

Yes, a supply of sharp #11 blades and a metal straight edge are the simplest tools to use to cut out your windows.  As previously stated, make your cuts in the grout lines of the model walls as that is where they would be located on the prototype.  Use multiple light cuts instead of trying to cut through in a stroke or two.  You may also find that using the backside of the blade tip will remove more material in less time.  Make both top cuts and both bottom cuts at the same time to ensure both windows are straight and parallel to the ground.

As the architecture of the area I am modeling seldom looks like the commercial kits based on mid-west architecture, I have had to scratch build many of my layout structures.  To better facilitate cutting window/door openings in sheet styrene, I modified an old vernier caliper (no dial or digital readout) I had by carefully grinding down the outside of the upper caliper jaw, tapering it to a fine point.  Since I did not remove material from the inside of the jaw, I can still use it to measure outside distances.  I first lay out my window and door openings on both the front and back of the sheet styrene using a sharp pencil.  I then adjust the caliper so that the sharpened jaw sits atop a pencil line when the unmodified jaw is held against the edge of the styrene.  After locking the caliper position with the lock wheel, I then carefully slide the unmodified jaw against the edge of the styrene while pressing the sharpened jaw into the desired scribe line.  Eight to ten strokes is usually enough.  I then flip the styrene over and repeat the eight to ten strokes on the back side.  This method creates clean straight scribe lines that are repeatable and perfectly parallel to the edges of the styrene.  With all of the scribe lines cut front and back, I then go back and cut through the styrene using a few more strokes of a hobby knife.  Finally, I use jeweler's files to clean up any rough edges.

I have used the caliper cutter method to model multiple strorefont window frames from a single piece of styrene sheet.  If I take my time and make all of the scribe cuts before making any of the cut-through cuts, I find I can make straight, square and realistic looking storefront window frames as thin as 3 HO scale inches thick.

As far as painting styrene, I usually clean the model using glass cleaner and dry it with paper towels.  I'll use my compressor to get any water trapped in the corners.  I follow that by shooting the entire model in rattle can automotive primer.  I have yet to find a brand that damages styrene.  I generally use craft paints to apply the color coat(s), either by hand or by airbrush.  Yes, you CAN use craft paints in an airbrush as I have been doing so for structures and rolling stock for years.  I normally use an airbrush when I need a smoother finish such as paint over metal siding.  I'll use a brush if I want to use brush strokes to add more of a woodgrain look to a structure or use a stippling action for a lot of texture to simulate stucco.  I try to buy only flat colors so I don't need to mess with clear coats.

Hornblower

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Posted by doctorwayne on Monday, March 29, 2021 5:09 PM

Traincraft199
1. What's the best way of cutting plastic cleanly without damaging it?

A lot depends on the plastic...I have some of Walthers brick sheets, which I believe may have been from their modular parts, and cutting them with a knife of any sort is difficult, as the plastic usually shatters...perhaps it's from a bad batch. 
For most styrene plastic, a utility knife works well.  For smaller windows, I prefer to drill holes near the corners of where the windows will be, then use an X-Acto #11 blade to simply carve away material to create the opening, then clean it up with suitable files.
Another option is to drill the holes, then use an X-Acto Key-Hole saw blade, which will fit in the X-Acto handle, to cut the opening.  Again, finish-up using suitable files.

Traincraft199
2. What type of paint should I use that won't cover up the molded brick details?

For colouring prety-well anything, my first choice would be an airbrush, which will allow very precise control of how much paint is applied.  I use both acrylics and lacquer-based paints, and usually create the colours I want by mixing them.

Airbrushing requires a bit of a learning curve, but once mastered, you're unlikely to ever revert back to spray cans - better control, better coverage, and less wasted paint, too, a real consideration given the current prices.

The brick in my home town was a very distinctive orange, so I usually use orange paint of some sort, modified with a little red or maybe brown or black, depending on the look I'm seeking.

Here's a Walthers kit for their Greatland Sugar Factory...I've re-purposed it as the Tuckett Tobacco Co. Ltd., and used both of the long walls to create a bigger structure... on my around-the-room layout, nobody sees the plain .060" sheet styrene which forms the back walls of such structures.

This is the just-painted results...(click on the photos for a larger view)

...and after applying pre-mixed drywall mud to represent mortar...

...and after a little clean-up...

...followed by a little weathering using well-diluted water-based acrylic paints...

This one was built from two Walthers American Hardware kits, with most of the walls used on the visible side...

...which, after painting the concrete areas, got the mortar treatment, too...

...after some clean-up, I used diluted India ink to add some weathering...

Unfortunately, it's somewhat dirtier than I wanted.but I won't bother re-doing it.

The brick colour that you want could be pretty easily done using orange paint, tinted with a little black to give the orangish-brown look of the real one.

Wayne

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Posted by DSchmitt on Monday, March 29, 2021 5:46 PM

mbinsewi
A supply of #11 blades for your hobby/Exacto knive, layout the window opening, follow horizontal brick joints, and scribe away.

Mark windows following brick joints.

Drill small hole inside each corner.

Scribe along metal straightedge using multiple shallow strokes using scribing tool or point of blade turned backwards (easier to control than cutting).

Scribe a little inside of final edge and finish with sanding stick.

I tried to sell my two cents worth, but no one would give me a plug nickel for it.

I don't have a leg to stand on.

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Posted by hornblower on Monday, March 29, 2021 6:25 PM

Great looking buildings Wayne!  I used the exact same technique to double the size of my Greatland Sugar kit main building (the small warehouse was built as designed and is placed to one side of the main building).  I especially like how well your mortar lines turned out.  My mortar results have always been hit or miss.

Hornblower

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Posted by doctorwayne on Monday, March 29, 2021 6:38 PM

Thanks hornblower. 

The pre-mixed drywall mud was put on using a rag over my finger tips, then allowed to dry.
Once dry, the structure was taken outside, then a clean rag was used to rub-off the excess.  Use your fingernail (in the cloth) to remove the built-up areas, which tend to collect adjacent to three-dimensional stuff, such as the the window sills and pilasters.  For really tight spots, the tip of an X-Acto blade works well.

Wayne

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Posted by Traincraft199 on Tuesday, March 30, 2021 10:34 AM

Cutting is done! I messed up a couple times but I'm happy with it.

Does it matter what airbrush I use? I already have a gravity feed one that seems to work (I tested it with water)

What type of paints should I be looking for or avoiding? krylon acrylic maybe?

 

Building my first layout, 4x8 contemporary urban area in HO scale 

  • Member since
    October 2007
  • From: Fullerton, California
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Posted by hornblower on Tuesday, March 30, 2021 3:52 PM

I start with a base coat of cheap automotive primer in a rattle can. I like to use inexpensive craft paints for the color coats.  You can spray these paints in an airbrush if you thin them to the consistency of milk.  Also note that you may need several coats to get the desired coverage from the thinned paint.

Hornblower

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