Tutorial: Gap Filling Part 2 - Largers Seams on Styrene

Part two of our tutorial on eliminating seams in styrene deals with pieces that fit fairly flush, but still have a larger divide than can be filled easily.
So last time, in part 1, we looked at how to eliminate very small, hairline type seams with parts that fit very well together. Today, we're going to look at ONE method of getting a seam that's just a little more stubborn out of the way.

So you've glued the piece together, and though the part fit is as tight as it can get, there's a very small gap. Large enough that just carving down with the dull blade of a knife won't fix without doing some serious digging. Basically, its too large for the first part to be effective, but not quite to the point you want to mess with putty and the issues that come with it. Here's one for an example:

So we're going to assume you've followed the first part and already glued and clamped the piece together, and you're left with this smaller gap. This method is MOST effective for smoother/flat surfaces. It can be adapted for irregular surfaces, but if you're dealing with a textured surface, we'll revisit that in a different tutorial.

STEP 1:
We're going to utilize the properties of styrene cement even more fully this time. The first thing I do when I'm presented with a seam like this is to get some 220 grade sandpaper and sand the whole works down to an even level. Resist the urge to "blow off" the dust, because this accomplishes a lot of different things. There will most likely be a drop off from one piece to the other, this step will level that potential unevenness down. It also fills the crack with styrene dust...see where we're going yet?

STEP 2:
Now, I take my cement and brush a layer back over the gap. This reinforces the strength of the piece, and also melts the styrene dust trapped in the seam, making the plastic itself work as a putty, but with much better adhering properties. This step really only works with brush on cement...any squeeze type cement won't even the styrene out. I drag the brush across the gap. This helps thin the cement out, and not "sit" on top of the piece, while forcing capillary action to make all the small dusty pieces adhere to each other.

 

STEP 3:
You don't need to wait overnight for this to dry, usually 1-2 hours is plenty if you've used a thin enough layer. Now we repeat the process of sanding with 220 grit sandpaper. You might consider starting at 320 if the surface is smooth enough, but I've found its a LOT of work to start at 400 grit. You'll eventually get a feel for where to begin on the scale, but for most first steps, I give everything a good polishing with 220 grit to get any crazy burrs off. Whichever you start with, move on down gradually. My method is usually 220>320>400>600>800 (occasionally). Once you get down to 600, unless you're dealing with natural metal paints or hyper-smooth finishes, going all the way to 800 is overkill. Once you've gotten down to the 600 grit of sandpaper, I'll dip the 600 grit in water and give it one last pass to really smooth it out, and there you have it! No more seam.

 

Next time, we'll get into some alternate methods. Thus far we've only visited ways to hide seams with the materials you're already using. Next we'll look at a few other options...putties, pastes, and even superglue! I just have to find a kit to use those on. Until next time!