Filler for scratches and seems ?

[rickd13]

I looked at other threads on here about filler, but I'm not sure I understand. What is CA filler? The problem I have is, when I scribbed the panel lines the knife slipped and made scratches. How should I handle these? Can I just put a coat of liquid cement over them and wait until it dries and then sand them? Another question I have is, how do you fill the seems you get when you glue two pieces together, like the seem created by gluing the front and back of a seat together?

[sportandmiah]

Some use CA (superglue) and when it dries, sand it down, leaving a smooth finish. To speed it up, buy a CA accelerator. I use superglue versus putty on.scratches and filling seams.

[weasel]

or, use a 'spot putty' , the red stuff, OR 3M makes a 2part 'sputty' that sands/feathers nicely...i've found that CA sands 'hard', sometimes you end up taking more plastic than needed to 'smooth out' the CA filler...

[hooknladderno1]

Rick,

There are as many different ways to fill seams and scratches as there are modelers. Prevention is the first step. If you know that you are scribing panel lines, use some of the old Dymo label tape. It is a hard, thick plastic tape with an adhesive backing. It will conform to curved surfaces. I also like to lay down a few layers of painter's masking tape to protect the surface. Enough about prevention. I prefer Evercoat two-partpolyester glazing putty. One can will last you a lifetime of modeling. It is available at any local auto body supply store, or on the Internet. One Internet supplier is TCP Global. As far as seam filling, two suggestions. Sand the pieces flat where they will mate together. Apply Tamiya Extra Thin cement. This is a thin solvent type glue. Squeeze the parts together, and/or apply a rubber band to hold them. The plastic should ooze slightly at the join line. Once dry, you can lightly sand to avoid having a seam to fill in the first place. Hope this helps.

David

[rickd13]

Rick,

There are as many different ways to fill seams and scratches as there are modelers. Prevention is the first step. If you know that you are scribing panel lines, use some of the old Dymo label tape. It is a hard, thick plastic tape with an adhesive backing. It will conform to curved surfaces. I also like to lay down a few layers of painter's masking tape to protect the surface. Enough about prevention. I prefer Evercoat two-partpolyester glazing putty. One can will last you a lifetime of modeling. It is available at any local auto body supply store, or on the Internet. One Internet supplier is TCP Global. As far as seam filling, two suggestions. Sand the pieces flat where they will mate together. Apply Tamiya Extra Thin cement. This is a thin solvent type glue. Squeeze the parts together, and/or apply a rubber band to hold them. The plastic should ooze slightly at the join line. Once dry, you can lightly sand to avoid having a seam to fill in the first place. Hope this helps.

David

Thank you for the advice. It was exactly what I was looking for.

[Mike Kucaba]

Generally that large can of putty will go bad before you use even half of it.

[wraith]

Some use CA (superglue) and when it dries, sand it down, leaving a smooth finish. To speed it up, buy a CA accelerator. I use superglue versus putty on.scratches and filling seams.

Super glue is one of my favorite tools for modeling. I use it to glue most parts together and also use it to fill in scratches and such. Sometimes when i need to fill a hole I will use Superglue gel. Lately my "filler" for low spots or sinks from glue on gluebombs is super glue and the fine plastic powder from my sanding. i acutally sand over a container now and keep as much of my powder as I can. So far this method has worked really well for me!

[Art Anderson]

First some definitions: CA is the quick acronym for "cyanoacrylate" glue, or "Super Glue"--much easier to say and to write or type. CA glues don't dry in the common definition of most all glues, rather they "crystallize", which reaction is triggered by one of several "triggers"; pressure as in pressing two parts together with CA in between, heat caused by adding some chemical or powdered material such as talcum (baby) powder or baking soda. or even moisture (get some on your fingers and the moisture in your skin will set the stuff pretty quickly!).

So called "2-part putties" are in fact a mix of polyester resin (think "fiberglas resin" here as that is what 2-part catalyzed putties are made from), with a finely powdered filler added to thicken the resin to a putty consistency. To this, a catalyst, or hardener is added, mixed in thoroughly in order to cause the resin to catalyze or "set up" hard.

"Evaporative putty" is almost always a putty in which the base is lacquer, most generally being described as very thick lacquer primer. These putties are not catalyzed, but depend on evaporation of the lacquer thinner to set up hard. Unlike CA glue or catalyzed putties, however, lacquer-based putties do shrink (they have to!) as the evaporating liquid reduces the volume of material.

All have their uses, frankly!

For major filling, nothing beats catalyzed, or "two part" putty. The stuff will not shrink perceptively, although it does upon going from liquid to hard, but that shrinkage generally is less than 1/10 of a percent, so small as to be imperceptible. AND, once the stuff is hardened, no further shrinkage is possible, as there are no solvents which will evaporate to cause any shrinkage, period. However, catalyzed 2-part putties don't always adhere tightly to polystyrene (the plastic from which our model car kits are molded), so some work before hand to give the plastic some "tooth" to hold the stuff is a good idea. Automotive primers, lacquer based, are good for this, as well as roughing up the surface of the plastic. I've had great results over the years by driling numerous holes in a body panel on a model car, to allow catalyzed putty to push through to the back side, thus creating almost a "rivet" effect which will hold the putty in place just in case. This sometimes inability to adhere tightly to polystyrene has cropped up for me when "feather-edging" puttied areas, where the putty gets sanded out to meet the styrene surface. If I experience any "chipping" there, a quick application of a bit of CA glue along the 'feather-edge" fixes, and prevents further chipping. With putty, I always look for "spot and glaze" putty, which is the finest grade of the stuff there is, meant for filling small scratches and gouges, not major filling of dents.

CA glues, as described above also do not rely on evaporation, but rather a crystallizing reaction to go from liquid to hard, again, no shrinkage. However there is a possible problem down the road when using CA for filling any large areas, and that is "blistering" of the finished surface. I experienced this years ago, when re-contouring the roofline of a couple of conversions for resin-casting masters, and used some very fine fiberglas cloth to not only provide thickness, but also to reinforce some "butt jointed" seams in the bodywork. Apparently this was caused by entrapment of at least minute bubbles of air underneath the surface somewhere. It was more an irritation (given that resin casting masters aren't fully finished model car bodies, just raw work done for the purpose of making rubber molds) than a disaster, but it did raise a red flag for me.

Now, a bit about tools, and techniques:

Have you ever visited an auto body shop, seen how an auto body technician works down a large puttied or leaded surface? They don't use small tools, and for that matter, they don't often use just their bare hands on sandpapers to smooth or level out such work, not at all! Rather, they use very large, flat tools, either as a sort of "cheese grater" (not at all unlike what one uses at the kitchen counter to grate cheese, or cabbage for cole slaw), a very coarse sort of file, or a flat, "board-shaped" metal tool which holds coarse sandpaper, all of which have the effect of "bridging" the area that is puttied, leaded or otherwise filled to smooth it out from "metal to metal". No clearing away the fillers which in the case of 1:1 bodywork are far softer than the sheet steel body panels being repaired (quite the reverse sometimes from what we as modelers experience!). In our case, such "larger, flat tools" include flat needle files, or sanding boards (either from the cosmetic aisle as fingernail files or boards) or homemade ones (sandpapers glued to popsicle sticks (make sure those are flat, straight and true though!--or glued to thick strips of say, Evergreen styrene). For final sanding of say, puttied in file scratches or tool gouges, sandpaper often is the way to go, but fold that 400-grit Wet or Dry sandpaper several thicknesses thick, so that your fingertips don't compromise your work, this multiple thickness of sandpaper will spread the pressure from your fingers out over a larger area. Of course, it should go without saying that you want to slow down, not try to remove a lot of material in a too-short time period--PATIENCE is your friend here.

A note about files: Needle files can be a model builder's best friend, and they are not expensive! I've bought needle files for as little as a dollar apiece, even as little as $6-$7 dollars for a set of 12 at real car shows and swap meets, at those huge tool dealer tents one finds there. The needle files that get the most use from me are flats, half-rounds, even the occasional "rat-tail" or round ones, that are tapered. It takes some time, some learning to figure out how to use them to the best advantage, but again, patience is key, not trying to remove too much material too fast.

All the technical stuff I've written here comes from about 50 years of working with putties and fillers of one sort or another, and the techniques of finishing come from experience as well--something like 250 semi- to scratchbuilt models of Indy cars over a 20 year period, numerous factory stock conversions, even a few completely scratchbuilt model car bodies over the years. I hope what I have written here helps!

Art

[wraith]

Thanks for all the info and the outstanding write up Art!