As I am building my “practice” models ( Old kits from swap meets that I got cheap ) to get my skills reasonable again, I came upon something I could not figure out how to do last night. I was dry fitting a canopy ( very old Hasagawa fw-190A, 1:32) and started to clean the clear part like I have done for every other part so far. Well, I used my dedicated sprue clippers to get the sprue cut off as close to part surface as possible and then tried to carefully use my #11 blade to remove the small remaining amount. I was able to remove the remainder without scratching the clear part, but the cloudy area of where the sprue was attached remained, despite it being level with surrounding clear part. Since this was a practice model for me, I tried Brasso, to polish it and it help a bit, but I was wondering if I could get some suggestions to try here - I would like clear canopies when I build my other planes!
I don’t think you can get rid of it, short of sanding way down past it, and that would alter the fit of the canopy. I believe it is caused by the stress of cutting off the sprue. I don’t worry about it, as that area is usually covered by the painted frame and won’t show when the model is finished.
I would seriously curse a kit that molded a sprue gate on the actual window portion of the clear part. I’ve never seen this, like Chuck said, they are on the edge or the frame lines that get covered by paint anyway. Otherwise you’ll have to polish it out then dip it in Future to minimize the crazing.
With clear parts, it’s better to cut the sprue a little further from the part and then file/sand the nub flush and polish if required.
The clear styrene used to mould these parts lack the fillers and plasticisers that are used in the “normal” parts. As a result, they are less flexible and far more brittle and are prone to cracking and crazing.
If you clip the sprue too close to a clear part, you risk the propogation of cracks or stress lines into the part or the very real possibility of taking an unintended chunk out of the part.
A flat “needle” file from a modeler’s file set does a nicer job than sandpaper. And, rather than polishing, I find a bit of future does as good a job as polish. And a pox on kit mfgs that design molds with a big sprue attachment point to the surface of a transparency rather than an edge. Not many do these days- most seemed to have learned.
Thanks for the suggestions - The kit I am building here is quite old and I have indeed noticed my recent kits do not put the spru into the “window” area - this Hasagawa kit is very old and the clear Sprue was massive in size, and caused a big area of non clear. I used Future on it and it is better, but still is a bit of annoyance. To those who say polish, what would you reccomend to polish with?
It’s only a “practice” kit to help me get used to modeling again, so I am not terribly upset, I am really asking to learn here
One thing to keep in mind is that plexiglas used to weather very rapidly in sunlight due to UV damage. Current aircraft have UV stabilized plastic, but the older ones like WW2 acquired a haze pretty rapidly, so on a plane of that vintage and older, if you weather the finish on the rest of the plane, a hazy canopy (and even a few cracks) is not unreasonable
You can polish the clear. Several manufacturers have a polishing stick among their line of sanding sticks. The one I’m referring to is a single stick with three different grits, one being white, on the same stick.
Since you’re working in 1/32, it may not be very hard to polish away the blemish, smaller scales can be more difficult.
You use the rougher surface to sand away the excess, the white surface to begin the polish and the final surface to polish the surface smooth. I’ve had success with this stick and use it often. It works well enough to disappear under a Future coat.
This technique may distort the view through the canopy somewhat when viewed at certain angles, but it beats a visible mar on the surface.
Give it a try if your situation allows it. If not, Don’s weathering idea above is an elegant solution.
Listen , if the sprue interfered with the window or canopy clear section here’s what I do .Very carefully take the part after cutting and look at it with your magnifier .You’ll see a myriad of tiny cracks .
This is the " Foggy Bottom ’ area . Now very carefully , so’s not to cause the glue to run , Take the liquid glue and put a little drop on the edge of the spot .
It will seep into those cracks clearing up the area somewhat . Now wait a day and sand and clean up the area as usual .You will find the spot gone or almost so . Works for me ! Tanker - Builder
