I'm right there with you DeafAviator. Definitely one of the modeling skills I need to work on.

I've read articles. Watched videos. Asked for tips and I'm still not where I want to be.

It may not be any help but one thing I found is that in some cases I was removing too much of the putty. In essence I was back where I started or worse.

Hello!

Well I used to have that problem too - and tried many one-component putties with no good results. Thing is, those shrink while drying. So when you sand the surface flush, they shrink some more and what was under the putty shows through. And they seem to dry forever. But then I read on the forums here, many modellers dissolve leftover plastic - sprue in lacquer thinner (acetone, MEK, stuff like that) and use that for a putty. I thought I'd give it a go. I used a nail lacquer bottle with a brush to do it, and for me it's a hit. You get stuff that's cheap, available anytime, and has the best possible adhesion to plastic there is. About the only disadvantage to it is the drying time - from the application it's best to wait at least 24 hours until you start sanding it smooth. But then it already has done all the shrinking, is just as hard as the surrounding plastic and sands and feathers just great. One cycle and you never have to worry about the spot anymore.

The alternative would be some two-component automotive filler, or CA glue - straight for smaller things like panel lines, or mixed with baking soda for bigger things (just heard about it, haven't used it myself yet). A thing to watch is when the filler is much softer or harder than the surrounding plastic - funny things can happen while sanding then.

It's also good to wrap a small piece of sanding paper around an eraser - to make a mini sanding block and sand wet - gives you a more even surface.

Hope it helps, good luck with your projects and have a nice day

Paweł

I use CA(super glue) exclusively for filling gaps and seams. I haven't used putty for years. Like modeling putty, CA also shrinks as it cures but the great thing about it is you can spritz a little accelerator on it and it will begin to cure instantly without shrinking which means you can begin sanding or filing it immediately. CA fills the seam better than putty which is why so many model builders like using it for that purpose.  If you do decide to use CA, make sure you use at least a medium viscosity formula. The thin CA would require numerous applications to fill the seam so it's not practical for that.

Thank you, DeafAviator, for bringing this up! I have been having a hard time with it, too. I haven't tried the MEK/sprue yet but may. Don't you have to be careful about this mixture eating into the piece you are filling?

One thing about using super glue is that it is a bit harder to sand smooth. I used to use super glue for seams but thought I would try putties for easier sanding.

BTW make sure the seam is actually cemented together. I've puttied and sanded seams a dozen times and they would not go away. Found out later that the seam wasn't glued and when I'd put pressure on it with the sanding stick it would 'pop' and I'd end up with a crack again. Worst situation was on a 1/72nd B-29 - the long seams on the top and bottom of the fuselage kept popping loose over and over- took me a while to figure out this was what was happening.  

The best method I have found is using either Tenax or Plast I Weld applied with the Touch n Flow applicator. For joining fuselage halves as an example, I run the tip of the Touch n Flow applicator along the seam and within a few seconds, the glue melts the plastic and creates a solid join like welding it together. I squeeze just enough to force a little ridge of plastic on the seam and when dry, it's easily sanded and buffed to a complete invisible join. If you have a larger gap then thick CA and even mixed with some  micro balloons to create a thicker more filling goop will work. When dry, sand out to a smooth join.  

As people above have mentioned, there are two problems.  First is the seam is not adequately cemented/glued together. In some cases it can just be reglued. In other cases, some kits do not have strong enough parts and maybe too thin of a gluing surface. In some cases you can use strip styrene to make a "flange" inside the joint that will, after the joining, bridge the seam making it much stronger.

The second problem is filling the seam but not level.  When applying the filler, make sure you mound it up a bit higher than the surrounding surfaces.  Be sure it has fully set.  Then, when you sand or file the seam you can get a decent looking seam.  With some fillers that take awhile to set and shrink a lot, you may need two coats of filler.  Primer should reveal if the seam is properly filled and smooth before you apply color coats.

In addition to all this good advise consider that sometimes the sanding medium is too coarse or you may be applying too much pressure which can actually sand filling material out of the seam ever so slightly.  Remember that putties and paint fillers like Mr Surfacer are not as dense as the plastic and will sand out more rapidly.

Next time try using a finer grit sanding stick or pad and use very light pressure.  Wet sanding also works better IMHO.  It takes longer using fine sanding mediums but typically you'll get good results.

And I'm really talking about sanding over putties and Mr. Surfacer type fillers.  With CA glue you do need to be a bit more aggressive.

The trick to sanding cured CA is to use a flat jeweler's file to get the bulk of the cured CA then the sanding stick comes in.

Thanks guys I will keep trying with some of your suggestions. My biggest issues aren't actually joint seams but actually the type of stuff like filling panels and gouges in the surfaces... but It's all the same really. But like I said I will keep trying! I think I am just being too aggressive, probably.

What type of putty or filler are you using? I find Gunze's white putty or Mr. Dissolved putty very easy to sand and blend in, without shrinking or flaking off. Its all I use to fill in sink marks or other suface defects.

I've had good luck using the regular ole Tamiya Grey putty. I smooth it out with acetone (nail polish remover) and Q-tips. Let it dry. Sand it smooth with Micromesh (usually 3200)

I usually use needle files to sand filler in seams.  Downside is it clogs files quickly and you have to keep cleaning them, but ithey do a great job. They take off material rapidly, but leave smaller marks more like very fine sandpaper.

Me too seams drive me nuts there is one more method I'll try on my next plane build it usese baking soda and thin super glue. Acording to video I saw you fill seam with baking soda then apply thin super glue,the baking soda act just like accilrator and dries the super glue as soon as they mix. Then you can sand and finish seam right away.             ON BENCH REVELLE F4 PHANTOM C/D 1/48             ACESES5        

For very thin short seams I use gel CA.  With the gel stuff you don't need the baking soda.

Filling is a technique I am far from good at, so really appreciate all of the great tips and advise here. Great thread and thanks, Todd, for bringing up the subject.

if it looks like a tight fit, say a gun barrel, use a lot of plastic cement and let it oozeup and dry, then scrape it down and sand. i use 3M body putty a lot (not the 2 tube version). if the seam is at a mard to reach place like between the fender and side of a tank hull, i run white glue along it and wipe it down with a damp Q-tip. may take 2 or 3 runs because the glue shrinks but makes a nice fill and paints well. any NATO tank barrel that goes south can be draped with a camo net. i have done that a few times.

I used to battle seams then I figured out the secret.

Patience.

Work the seam with your desired method and then leave it alone for a day to fully cure. Observe the seam for your desired look and then repeat as often as required to make it disappear. Wait another day for everything to cure. Repeat.

Once you are happy with the work primer it and let the primer fully dry, then reinspect the seam. Primer will reveal any problems. I've even used BMF (Alclad) as a primer because nothing shows shoddy seam work like BMF.

When the work is correct it may still look bad. You may see feathered lines where plastic, primer, and filler material are all visible at the same time, yet the seam will fully disappear under paint. When in doubt, primer again.

Patience, practice. You'll get it.

Hello!

With all due respect, you have to be careful with that - if you have too much patience, you may end up spending months on one seam in your model. If you have the misfortune and fill a rather large seam with generally avaialble one component putty, you can wait two weeks just to discover the seam shows through the primer. And again. And once more. Six weeks gone. That's how the thread started in the first place. Some people use two component putties - you just slap them on, sand wet and hopefully you're done in just one evening - can be done too!

But of course practice and patience ARE very important when modelling. Let's just not waste the opportunity to do things better and faster.

Have a nice day

Paweł

The one part putty I use sets in twenty to thirty minutes, the same as the primer I use, so an hour after I apply it (depending on how long it takes to smooth the putty) I will know if I need more work on the seam. I use auto body glazing putty and krylon primer.

It takes me a week to build a quarter scale fighter from start to finish. Depending on the kit the equivalent of three days of that time is spent on seams. My current build is the old Monogram TBD-1. I started it Saturday afternoon and yesterday it went through it's second and third rounds of seam work. I haven't worked on it today but the next bench session will be the forth and final round of seam work. Speed isn't a problem.

There are some really good ideas and suggestions here but I have a couple of observations to make.  If you use CA, get it filed/sanded down as soon as possible after it sets up - the longer it sets, the harder it gets (I once applied a mixture of baking soda and CA to the underside wing joint to an  1/72 and then went to summer camp at Fort Carson, Two weeks later came home and the joint was like a piece of granite!)  And if you need to apply a coat of putty that is more than 1/32 of an inch try to apply the putty in 2 or 3 thin applications instead of one thick coat (let each set up before applying the next coat).  

Wow guys thanks SO much! I'm sorry I haven't been as involved here as I should be - for some reason I stopped getting email notifications of responses.

I think my biggest problem is trying to rush through the seam work and not letting things set up, in combination with using too much pressure and sanding too much. I have been trying to experiement with some of the putties that can be "wiped" down (Tamiya or Mr. Surfacer with Lacquer or Perfect Plastic with water) but these seem to be a little bit finicky for me.

Patience, gentleness, and learning when to stop sanding are going to be my keys to success, it seems like. I am working on an F-14 and F-18 and they both have plenty of seams that I am working on for some good practice.

To answer one of the questions - I have used CA Gap Filling, Perfect Plastic, Tamiya white, and Mr. Surfacer 500. I tend to mix these up depending on the type of work I am doing.

Also, when you guys sand, say, Tamiya or Perfect Plastic, what do you use - straight sandpaper or pads/sticks? I am wondering of the "padding" of paper/sticks is hurting or helping, or if regular paper with fingertip application would be any better.

Also, how do I keel files clean? As Don said, they clog up incredibly quick but I do love using them for heavy work...

To keep files clean you can use a file card that you should be able to get at any home improvement store. But, as an alternative, I usually wipe the file off right on my pants. That works good enough for me.

JimNTENN

To keep files clean you can use a file card that you should be able to get at any home improvement store. But, as an alternative, I usually wipe the file off right on my pants. That works good enough for me.

File cards sold at most hardware stores tend to be too coarse to really do a good job on fine needle files. I found a dremel wire brush wheel with very fine wire, and use that to clean my needle files.  Also occasionally use one of those 3M kitchen scouring pads.

Do you actually run the dremel with that wire brush on the file or just use the brush by hand? I happen to have one of those...

Sometimes (slowly- both of my Dremels have good speed control) but more frequently I just grab the brush in my fingers and use it like a conventional file card.  Hardest thing to clean out is solder when I have been working with soldering brass.  Plastic and filler clean out fairly quickly, primer paint is somewhere in between.

I have no luck with CA so I tend to use putty.

Also, if using putty or something like it, mask the area to get it on as small a part of the model as possible. It makes a step, but that can be sanded off.