At a club meeting last night, the topic was seam treatments. I brought along a work in progress kit and demonstrated scraping as a technique to level and smooth seams after applying putty. Scraping is a centuries old technique of smoothing a surface used by machinists and carpenters. One draws a sharp edge along a surface with the blade almost perpendicular to the surface. I had never heard of anyone else using the technique before, but half of the attendies last night do use the technique. Yet no one seems to talk about it. How many people in this forum use it?
That’s my preferred technique for getting it close. I use either a straight or rounded blade depending on the contour of the area. Follow up with 1500 grit sanding sponge to take off the scratch lines. I find it much easier to limit damage to adjacent detail with scraping than gross sanding.
I should add that I generally use TET which tends to leave negative areas to fill with Mr Surfacer rather than positive extrusion on the seams. If one uses slower setting cements and squeezes the heck out of the seam, you can make almost anything fill in without putty and deal with the flash later. Of course, that comes at the expense of distortion, at times.
I used to use that technique, which I had always called “adzing”, but I always felt it removed a little too much material. I use Micromesh sanding sticks now for removing the bead of re-hardened melted plastic along a seam and rarely use putty. The Micromesh sticks remove just the right amount of material and do minimal damage to surrounding detail. Any tiny gaps that are left over get filled with tiny dabs of Gorilla super glue, scribbled over with an ultra-fine black Sharpie, and sanded again with the Micromesh sticks until all of the black Sharpie is gone. If I ever use putty, its always Apoxie Clay, and that gets smoothed out with tools dampened in water before it cures…no sanding or scraping needed.
I’m new to modeling. I made an irreversible error on my current build, a 1/72 B17. The booboo caused some seam mismatch. I had never scraped before but it allowed me to wiggle out of the problem.
I do it all the time - it’s my preferred method.
I generally use the scraping technique if I have, say, a ridge of material to remove. I use a curved blade & work carefully until I’m close enough to finsh with sanding sticks or pads.
I do this as well. Use a hot glue like weldon down the seam and sqeeze a bit. The melted glue oozes out a bit. After drying I use the back of an exacto to scrape.
Slower drying laquer thinner works well for this. When the squeezed ooze dries you have a prefilled seam ready to adz and smooth. No or hardly any filler at all.
I use it, though it’s not always possible, in every situation. It’s very useful building airplanes, for seams where fuselage halves meet, or tops and bottoms of wings.
I like the idea that the seam is filled with homogeneous material-the kit’s own plastic. So it should behave like the rest of the plastic. That’s why I like to use stretched sprue, too. That doesn’t mean I don’t use putties, but I recognize that a putty might shrink as it cures, and will likely need sanding, thereby damaging the surrounding detail.
I’m surprised you haven’t heard about it here in the forum, though, because I know it’s been discussed. Though it might not have its own thread, just mentions in build blogs or in threads about addressing seams. i know I’ve suggested it when someone asks how to deal with seams.
The homogeneous material really seams to be the best way when possible.
Sometimes I just can’t help myself…
I never scrape and seldom use putty. I use Plast I Weld solvent glue to melt the plastic along the join creating a ridge that is easily sanded smooth when cured overnight. I use multiple grit grades of sanding sticks to sand and polish the join. Even 0000 steel wool will do a great job at polishing out scratches on plastic.
That’s pretty much the same thing, though, PJ. The technique is really based on squeezing out that bead along the seam, and then removing it, when the glue has cured and the plastic is hard again. Whether we use a blade of some kind to remove the bead, or abrade it away, are just different flavors. I generally use a Nr 11 blade to remove the weld bead, then smooth it out with sandpaper, or a Flex-i-File, especially on fuselages and leading edges of wings.
I use essentially the same technique as PJ. I used to use the #11 blade, but found that its just an extra step that can potentially damage things, so I just use my Micromesh sticks to sand and polish the bead of melted plastic away.
I’ll use the scrapping technique on small stuff like fuel tanks and ordinance and if there is a big mismatch in fuselage halves. However, I’m always worried I’ll take too much off on large assemblies.
Its a matter of learning the right downward pressure. The lighter the pressure, the less you take off, like filing or sanding. Like any technique, practice helps to gain experience. You’ll get the feel pretty quickly.
On one of the Flory videos, he showed a set of scrapers with various curves and angles that can be used to scrape seams along curved surfaces without leaving flat spots. I believe they were made my U-Star. I haven’t been able to find them at any of the usual US suppliers and not sure I want to order from eBay. Seems just as likely I’ll get a flattened beer can from China instead of the real thing. Nice idea, though.
I think if you really get into scraping, a set like that would be of some benefit, like in scraping the inside of a curved surface. But for flat surfaces or outside of curved surfaces a good rigid knife blade works fine- no need for fancy stuff. While a #11 blade does work if you are careful, it tends to bend a bit too easily and can chatter. I really recommend a stiffer blade.
Funtec out of Japan makes a tungsten carbide scraper bit that mounts in a regular pin vise handle. It works good for getting rid of mold seams on plastic, resin, and cleaning up putty. Its solid and doesn’t chatter on the surface like a regular hobby knife blade. Gouging isn’t an issue since it doesnt have a knifes edge, unless you exert to much pressure.
