Monday, March 25, 2013

Multipass Tutorial - Step 5

In this step, we prepare the dome that is used as the "button" for the Multipass. Key to the success of this step is a simple battle of psychological warfare. In the process of cleaning up the dome, it gets really trashed. The sanding an filing ruins the transparency of the dome and makes it look awful. But have faith, and stay the course. By the time this step is done, the dome will be as clean and see-through as it was when you started.

I was once convinced that the dome for the multipass was a google eye that can be found on stuffed animals and such. I'm no longer convinced of that for a couple of reasons. First, plastruct parts are a mainstay of any prop/miniatures shop. It is very likely that the propmakers on the movie had plastruct stock sitting around. Second, the domes I use are precisely the right size for the doughnut shape that appears on the multipass, as scaled from a known critical measurement on the pass. Third, to get the google eye to work in this context requires a lot of labor. So much labor that I have decided not to include a tutorial on how to make it work. Frankly, it's very difficult, very problematic, and does not provide results as nice as you get with the plastruct dome.

Here is the dome as it comes straight from Plastruct. You can barely tell from the picture, but the main problem with this piece as it stands is the ejection port nipple on the top of the dome. It's basically a big hole in the top of the dome that is created when the part is made. The first thing we need to do is remove this so that the dome appears smooth.

Note: The removal of the nipple is totally optional. if you don't care about the nipple, then you can skip the first few steps of this part of the tutorial. Go straight to the part where you put the yellow vinyl on the back. In fact, there's even a shot in the movie of Korben's pass where it looks like the nipple is in tact. So it's really up to you.

The first thing I did was file down the sprue on the side of the dome. I did this using a hobby file. The dome is a tiny little bugger, and one of the more challenging aspects of this part of the process was simply getting my fingers around it in a way that will allow me to attack the dome with whatever tool I'm using. I do not recommend using a clamp or clasp to hold the dome in place, as the plastic is pretty soft and will damage easily.

Now it's time to wear down the nipple. I started in with a flat hobby file and basically just filed away the top millimeter or two from the dome. Keep filing until the nipple disappears altogether. You'll be surprised at how deep it goes. After you sand off the main lip, there will still be a small white dot in the middle that will take some work to get rid of. Keep going until it's totally gone. Don't worry about the shape of the dome and how it's changing. We'll fix that later.

This picture shows the dome after I filed the nipple down. It looks like there's a flat plateau on the top of the dome. There is! Our next task involves fixing that.

I start out with some 220 grit sandpaper. I wouldn't recommend using anything lower than that, as it may carve lines in the dome that will be too deep to polish out. If you want to start with a higher grit, you'll just need to do more work. Basically, with the 220 grit paper, I reshape the dome. I smooth out the transition from the dome to the plateau I just created in the previous step so that it resumes it's domed shape. You can also use this opportunity to flatten out the dome a bit more if you chose to.

After using the 220, the dome looks pretty foggy. We've scratched up the surface pretty badly. However, it has the proper shape, and that's what we're after.

This picture shows the dome after I hit it with some 1000 grit sandpaper. I went straight from the 220 to the 1000, and used water in the process. Wetsanding will always provide smoother results than dry. Just take a bowl of water, dunk your sand paper in it prior to use, then go to town.

Now that we've gotten any grooves out of the dome that were cut by the 220, and gotten the dome into the shape we want it to be, we're ready to polish it. Grab some colgate, a sock, and some water. You can probably use any type of toothpaste, I just happened to have Colgate sitting around. You know... for my teeth.

Place a gob of toothpaste on the dome, wet your sock with the water, and rub the thing down. You actually won't need to polish it that much to get it perfectly clear, assuming that you did a good job with the 1000 grit sandpaper. After rubbing the toothpaste on it for a minute or so, wipe it all off to see how it looks. Repeat if necessary.

I'm not convinced that the breath strips in the toothpase add any advantage!! hah! But hey, it's what I had on hand.

Here's a picture of the newly improved, nipple free, recently polished to perfection dome.

I've noticed that sometimes, the back side of the dome is not completely flat. I think this varies from dome to dome. I was not satisfied with the back of my dome, so I used the 1000 grit sandpaper to flatten it. I drew little figure eights with the dome in order to avoid wearing down one side more than the other. After it was flat, I polished it with toothpaste.

In the next few steps, we're going to give the button its yellow background. I use a piece of yellow vinyl, but there are probably a million different ways to do this. You could paint the back of the button, you could paint a piece of styrene and then glue the button to it, etc. Feel free to improvise.

In this step, I'm peeling the backing off the vinyl circle. This exposes the adhesive side of the vinyl.

Here, I simply plop the button down on the adhesive side of the vinyl. Assuming I haven't screwed up the dome, the underside of it should be pretty darn flat, meaning that I shouldn't have much trouble getting the vinyl onto it.

I now use an exacto knife to cut away the excess vinyl from around the button.

There you have it. One yellow dome.

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