What are you using to fill styrene gaps, and what are you sanding it with? I understand that whatever is used to sand with, it must be very fine.
How big of gap are we talking about here? I use 600 grit for sanding off glue marks etc.
We are not talking about something special, just want to know the basics of filling and sanding styrene.
Hobby shops sell a styrene paste made from styrene and high amounts of solvent for that purpose. One brand is Squadran Green body Putty but there is at least one other brand that is white. Easiest way is to spread some on a card or piece of wood and used a small stick or Exacto knife to place it where it needs to be. due to the shrinkage as the slovent is evaporated it may take two or more applications to bring the gap up to flush. This is easier than overfilling and having to remove the execss. It is alos easier on surrounding details. I built a square end PRR obs with the stuff by layering styrene like a wedding cake and rounding the mass with putty. It is ten years old now and still looks like the day I made it.
ndbprr,
When sanding it, how fine paper do you use?
This may sound nuts but when I need to “sand” styrene and Squadron Green putty and it needs to be super smooth, I sometimes use a stick of 1/4" square balsa wood. There is just enough tooth to it to be slightly abrasive, although it takes some elbow grease. If I added some toothpaste it would work even better – sort of like jewelers rouge. This might be a good use for the little tube of toothpaste you get “free” from the dentist after regular checkups.
Some people use balsa wood to clean track for this same reason – it is very slightly abrasive or rough in surface.
Speaking of dentists I wonder if those little Y shaped thingies with dental floss built into them – sort of fancy tooth picks – would also provide a smooth and nonabrasive way to smooth out a gap filled with Squadron putty. They sell them by the bag at the drug store. I have not tried this.
If the Squadron putty has been applied somewhat crudely I might first use an ordinary emory board to approach the rest of the surface, then switch to the balsa wood. You can cut the emory board with sissors to match the exact work surface you need.
Another thing that works pretty well is the Bright Boy I otherwise use to clean track – a pencil, ink, or typewriter [what’s a typewriter, daddy?] eraser can also work, with varying degrees of effort involved, but the more abrasive it is the more a single bit of grit can cause a scratch.
Dave Nelson
Squadron white putty, 320, 400, 600 paper and sanding boards. Scrapers like dentists use to pick out the details.
What are you modelling? If it’s the Moffat Tunnel portals, then you might not want a smooth surface. A coarser grain sandpaper would give you a rougher surface that might be a better representation of concrete.
If you really want a smooth surface, though, you can spray on some satin (semi-gloss) or gloss lacquer after you paint the model, if you’re using a flat paint. This is also a good preparation for decals, and may be used again after the decals are applied to protect them.
Great suggestions, I have a few places on some of my scratch built buildings that this would work well on prior to painting. Thanks
I’ve used Squadron Green putty with good results. Another method I sometimes use, is to dissolve scraps of sprue with Plastruct’s ProWeld. The resulting “putty” is then applied to the model and sets up hard. I haven’t noticed any shrinkage, but it sometimes sets up a bit too hard if there’s not enough ProWeld in it.
To level the filled surface, I start with a foam drywall sanding block from 3M. Then, I go through the various grades in my Testors’ sanding film pack. By the last film, the surface should be very smooth. Prime (if necessary) and paint as normal. I tend to apply primer sealer, since it helps prevent lines “ghosting” through the paint.
Not to sound like a “hindquarter”, but try not to have a gap in the first place. If you do, replace the part (with scratchbuilding in styrene, this isn’t very expensive…some of the time).
If you DO have a gap that you can’t get around, try to fix it. In general, you should be using some form of MEK-based liquid cement. The easiest way to fill small gaps is to apply more LPC until the joint between parts really starts to melt, and then wiggle the pieces around until the gap disappears.
If that doesn’t work, use a filler piece of the same material FIRST, before you use putty. If the gap’s at least .005" wide you can stick a shim piece of styrene into it, and try the LPC and squish technique. This generally results in a better, stronger, and less likely to shrink patch.
If you have a larger gap, try to work over it. If it’s a freelanced building try adding a new trim element over the gap, or even something like a gutter downspout.
If you HAVE to use putty, use a plastic-based one like Squadron Green or Miliput. Many modelers don’t like Squadron, since out of the tube it’s hard to apply, takes a while to dry, and shrinks. They don’t know how to use the stuff. The BEST way to use Squadron is by turning it into a slurry of LPC and putty. You can control how thick or thin the stuff is that way, it’s easier to apply, and it doesn’t shrink as much. You can even strengthen it by melting plastic shavings into the mix. Apply with something small, rigid and flat, like the end of a flat toothpick. The working time will be increased, it’ll stick to the material better, and it’ll actually dry faster.
I try not to sand, unless I’m flattening the bottom of a structure. Instead, I’ll SCRAPE an area smooth whenever possible. Scraping with a sharp blade is faster and yields a smoother finish surface (unless you want to waste your hobby time by wet sanding with 800-grip paper all day)
STYRENE filled gaps are a substitute for Atlas ‘insulated rail joiners’ and prevent expanding rails from ‘touching’ and causing shorts.
THE THICKNESS can vary.
BENEFIT is near-invisibility. TRADE-OFF is trimming to accomplish.
‘‘Trimming’’ is cementing in-place, cutting with exacto/filing, to match contour of rail.