What’s the best way to fill smallest cracks in seams?

I normally run a small bit of CA glue in there with a fine piece of wire.

I've recently been using Vallejo acrylic putty. Water washable until hardened.   Same kind of dropper bottle as their paints.

Spread some in joint, ive used a paintbrush on small areas.    Go back with a damp Q-tip and wipe the excess off across the seam.   When hard it can be sanded or buffed with a t-shirt

I hadn't heard of that product, thanks Ed.

Back to the OP, I use PPP (Perfect Plastic Putty) but it sounds like the new Vallejo product Ed mentioned is thinner and might be even better for the small seams you are asking about.

Hi Greg!

 I have been using Mr Primer Surfacer to do it. Remember they have three different thicknesses. The thickest rubbed over the surface and then sanded when dry works for me. Tanker-Builder

Hi TB!

I hadn't thought of Mr Surfacer. Another great idea for a small seam. Like you, I have all three thicknesses in stock.

I use a toothpick to apply Mr. Dissolved Putty. It is easy to sand after it is dry.

For really small cracks or seams I just use a small brush to paint some flat paint over it.  Then sand with fine paper.

You can also use white out tape to fill cracks and seams.  I've used it to seal seams on wing roots.  It takes paint well and is thin enough that it doesn't mask detail.

HTH

Doug

Greg

use PPP (Perfect Plastic Putty) but it sounds like the new Vallejo product Ed mentioned is thinner

I'll liquify PPP and fill to flush.

This is a common question-you'll find a good number of threads here that ask it.

For me, I use Squadron white, thinned with acetone.  I use two methods.

One is to apply the putty to the seam, then to use a cotton swab or an old paint brush dipped in the solvent to remove the excess.  I wipe across the seam, so as to leave the putty in it but to remove it from the surrounding area.

The other is to dissolve a blob of putty in a little glass jar (eg, old MM or Tamiya paint jars) with a couple drops of acetone.  I stir this with a toothpick, till it's consistent, then I use an old paint brush to apply it to the seam.  I call it my homemade Mr Surfacer.

I also use regular Mr Surfacer, too.

Another method I use on styrene kits is stretched sprue and liquid styrene cement.  I'll stretch a piece to an appropriate size for the seam, lay it on the seam, and flow liquid cement over it.

As far as Perfect Plastic Putty goes, it's great, as long as you don't get it wet after it dries.  Water will dissolve it an you'll have your seam back.  Wet-sanding is out.

Are the cracks in the plastic or the filler?

plasticjunkie

Are the cracks in the plastic or the filler? 

Good question.  On repeated reading, I see your point.

I use the Gorilla brand of super glue on a toothpick and touch it to the seam.  Depending on the depth of the seam or crack, I give the super glue anywhere from a couple of hours to overnight to cure.  Use a black sharpie to put a coat of ink on the glue and surrounding plastic, then wet sand until all of the black is gone.  Works like a champ, and you only have to do it once, as opposed to the usual fill-sand-fill-sand dance.  The best part is, if you missed a tiny gap that gets revealed after primer goes on, you can use the same technique, as long as you just touch the glue to the seam and don't try to spread it.  It will combine with the primer and harden just fine if its left alone to cure.  No need for fillers, the glue by itself does the job.  Basically, the only reason I prefer using Gorilla glue for this is that they seem to be one of the few manufacturers who has figured out how to make a dispensing tip that doesn't clog.