Saturday, November 24, 2007

First Pull Out Of The Mold!

Today was a really productive evening! If you want to scroll down to the bottom of the page to see the final results, please do. It's quite stellar, in my opinion.

But let's start from the very beginning. A very good place to start.

My order of 1630 arrived the other day, but it wasn't until today that I had a chance to unpack it. It's a 10 pound kit. Each of these gallon containers is about 3/4 full. That's a lot of 1630!

Why 1630, some of you may ask?? Why not just use resin? Why not just pour it solid??? Couple reasons, though the main one will hit a nerve with you Seinfeld fans.

One word.


One of the most interesting properties of 1630 is that it has almost no shrinkage. I think the data sheet for it puts it at .02%. That's amazing, considering most resins range from about 2% to 5%. Resin shrinks less if you're pouring thin, small pieces, but more if it's thick and huge. (That's what she said). For examle, your average resin handgun is typically 1/4" to 1/2" shorter than the mold it came out of. That's a big deal. On a gun the size of this one, you might lose an inch or two. I don't wan that.

So while 1630 is more expensive, and a bit harder to work with, you benefit by having almost no shrinkage. It also tends to bond to itself VERY well. Most resins to a decent job of bonding to themselves, but not always. 1630 also sands really well. It's good stuff.

My first order of business for today was to repeat something I did the other day. I poured resin into the detail pieces on the rifle. Why? 1630 is great stuff, don't get me wrong. But it's not super strong on the detail pieces. When you mix up a batch, it's pretty thick. The resin I use is only SLIGHTLY thicker than water when it's pouring. 1630 is more like maple syrup when you mix it. What this means is that it's less likely to get into all the tiny nooks and crannies that you tend to find in those little greeblie detail pieces. So I poured in the resin.

The instructions and labels for the 1630 mention that you need to shake well before using. What they don't mention is that you need to mix the HELL out of it before using. I shook the cans around for a few minutes before cracking them open. I put a stirring stick inside, only to discover that about 50% of the can was a thick sludge!!! It looks like that creature from "Skin of Evil". You know, the one that killed Tasha Yar?


The same was true for the other half. I spent about ten minutes trying to mix it by hand, and then gave up. I needed a paint mixing bit for my drill! I hauled down to Home Depot and picked a couple up. They were only five bucks each. I got two because I didn't want to risk contamination of either half of the stuff. Who knows, a few ounces of part A might cause part B to cure overnight or something. Didn't want to risk that.

Even with the mixing bits, it took me about a half hour of mixing to get all the sludge mixed into the stuff. Ten bucks well spent.

Another little hint for you readers. Whenever you deal with resin, and ESPECIALLY when you deal with fiberglass, wear gloves. For under 10 bucks, you get 100. Not only will they keep your hands clean, but it will save you HOURS of picking resin out from under your fingernails, under your sking, and wherever else the stuff might get. They're just gold. Go get them.

With my gloves on, and my 1630 all mixed, I went to work on the mold. I used chip brushes (.59 cent throw away brushes) from Home Depot to apply the 1630 to the mold. It's brush on kind of stuff. I only mix up a little bit at a time. The stuff turns thick in about 5 minutes. That's how much time you've got to push it into every corner, and up on every wall. It's not thick enough to stay on the walls, but we'll get to that later.

I placed a couple of R2 batteries on the inside of the mold to help keep it in place. It looks like this top half of the mold was stored upside down for a number of years, and as a result has a bit of a sag to it. When turned right side up as it is now, that sag turns into a bulge. (insert off color joke here). The batteries keep the bulge down. My theory was that once a couple layers of 1630 cured, I could remove the batteries, and the hard resin would keep the bulge down while I covered up the rest of the mold.

After a number of applications, it was time to switch gears and start laying in some fiber. I guess if I wanted to get slick, I should have actually used fiber glass. It's probably stronger, and lighter. But the smell of it just kills me, and I wasn't sure if I had a big enough supply on hand for the entire job.

So I just laid in the fiber with another coat of 1630. I'm using fiber that I picked up at Kragen Auto Parts. It's not the sheet stuff, it's the type that you can pull apart with your fingers. I like that stuff better. It seems to handle odd shapes with sharp corners better.

I start by pouring in some wet 1630, then I drop fibers on top of that. I usually try to have some order to my "drops", and try to get the fiber where I want it to be. Then I dab the brush into my cup full of resin, and dab at the fibers until they're nice and wet. You want to make sure the fibers are soaked all the way through.

The fibers add a ton of strength, but also keep the resin in hard to stay places. Like up on the walls of the rifle. Usually the resin just wants to slide down into the base, but with the fibers there, a bunch more of it stays.

Here's a close up of the tip of the gun, with some fibers sticking out to show you what I'm talking about.

After a few more applications, I was done. It took a bunch of time. I think it's very important to note again that I did this in a large number of small applications. If I tried to mix up a big batch of 1630 then get it all spread around, I would have failed. The stuff sets up too quickly, and you've got to work fast when you're trying to get it into all the corners.

And now I was at a juncture. With all the resin in the mold cured, I needed to decide what to do next. I had two choices. Demold the thing, or leave it in there. This decision is really related to how I plan on joining up the two halves of the mold. Do I want to do the join inside the mold, or once the two pieces are out.

Along the way during the work tonight, I decided that I was going to opt for the former. I was going to demold the gun in two halves, and join it outside. Why?? Because I'm not sure how the mold is going to hold up. For all I know, trying to pull the clamshell in half while there's ten pounds of resin inside could cause it to tear in half. I don't know how fragile this mold is that's been sitting on a shelf for ten years. I don't know how many pulls have come out of it, or how many more can. After what I saw happen to the mold for the detail piece, I was definately worried. So I figured it was time to demold.

And here she is!! It took me about five minutes of pinching and pulling to get this out of the mold, but at the end of the day, it came out pretty smoothly. To my surprise, there was ALMOST no damage to the mold. There was a tiny, half inch long, 1/64" high strip of rubber that ended up stuck to the gun, but that was it. VERY impressive. I was worried that one pull was all I was going to get.

Just for reference, I put the resin detail piece in place, to give the readers and idea of how it will all fit together. Looks pretty darn good.

I don't know how much I'm going to get done tomorrow, so I may wait until sunday to do the other side. now that I'm feeling comfortable with the materials and mold, I think that half will go faster.

Now that I'm done with this half, the mold can be returned to it's home, high inside my garage.

Time to seal up the 1630 too. I use a rubber mallet to pound the lids back into place. Not only does it get the lids securely on, but it doesn't crunch them up like a regular hammer might.

All told, it took me about 2 hours to get this half of the mold done. My knees are killing me!!!

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