streched sprue

On a previous article in FSN, the guy said stretched sprue is too fragile. He recommended fishing lines. Anyone tried it before?

I began stretching glass tubing for my science projects and the principle is the same although requiring a Fisher burner or a flame spreader on a Bunsen burner tube. I learned to let the glass hang to keep it straight so I stretched to my arms length, tipped everything vertical while maintaining tension and then hanging up the tube in a small spring clamp which I hung over the end of my bench.

With sprue I use pieces of sprue which have higher quality plastic in them and have good, 5 or 6cm long blemish free, round or square runs. I cut them into the longest run I can and store them in my spares box. When I stretch I stretch over an alcohol lamp (there's that old science stuff again) and do several pieces to get a variety of sizes which I can measure with a micrometer if accuracy is needed. I hang them from clothespins which work well because the plastic is so light.

You can then cut them into lengths for the spares box and you are ready to go.

Sometimes I need a bulbous end for a light bulb so I use clear acrylic tube and hold it near or against a hot light bulb until the end begins to form a bulb. You can also put flat nail or bolt ends on sprue the same way. I haven't tried making rivets yet!

Lots of fun and lots of applications,

It's best if you can be shown how to do this. The late Jim Jones (not THAT one) but the one who had that fantastic Shinano Japanese aircraft carrier in the FSM Showcase in December 1989, taught me how. I've been limited in stretch only by the spread of my arms.

I mastered the art of stretchin sprue a while back... and even though I haven't needed any in recent years, I STILL have some mighty fine pieces I stretched, sitting in a parts drawer all by themselves, just in CASE I may need some and don't have any sprue handy! (Yah, like that would EVER happen!)

Practice makes perfect and builds up a supply for future model uses! Definitely dip it in the water to cool it!

When then need comes around for anything that stretched sprue would do, I usually plug the hot glue gun in. If you start a small blob on the workbench and pull it away quickly, you get the same effect as if you were stretching sprue without the candle etc. also a small needle heated on a light bulb will give you enough heat to attach the "string" to what you want without any glue. This only works for very thin "wire" looking stretched pieces. Bigger than that, stretch some sprue.

QUOTE: Originally posted by goldenretriver Question. Are toxic vapors created when melting sprue over fire? Just wondering Mike M

If it ignites, yes. Scented/colored candles also can give off traces of metal, etc., so it is best to use an small, unscented candle as a heat source (plain votive candle for example) or some other clean burning flame. I bought a small oil lamp at a craft store for about $3 and a quart of plain lamp oil for another couple of bucks. Now I have a controllable flame, and with the lamp chimney on, I can rest the sprue at the same heighth every time.

Question. Are toxic vapors created when melting sprue over fire? Just wondering

Mike M

Phil, I also save as much of the longest and thickest pieces of sprue for awhile, then when I have a sizeable amount, I sit for awhile and just stretch it. I try for the thinnest pieces I can get, but if it comes out thick, I still save it. The thicker pieces are good for gun barrels, struts, and other thin items in 1/72 scale. I then cut every piece into 1 to 1 1/2 foot lengths and save it all in a long box that formerly held a ship kit. I think I have about twenty or thirty stretched pieces at my disposal right now; very convenient!

No matter how thick or thin you stretch the sprue, keep tension on it until you feel it tug back. That's the best way I know to say it, I'm sure it's something to do with the plastic cooling and it's a very subtle contraction, but I can feel it and I'm sure others can too. I'm glad Mr. Crockett mentioned cooling the sprue with water. I've alway wet my finger tips in the bowl of used decal water that seems to always be on my work table, and then run the length of the stretch, carefully maintaining tension. I've always thought it made sense to cool the stretch, but I've never heard anyone else mention it, thanks. Probably the most important tip about stretching sprue is to use a good, clean and very round piece of plastic. Hard Japanese plastic seems to work best for me, it doesn't break under fire as easily as softer plastics. I save good lengths of plastic from old kits. The Great Herself calls it "Yet another box of useless junk," but I know better...

When stretching sprue (extremely convient, when you get the hang of it - great for all sorts of detailing) I take the time to sand/scrape mould seams off the spruce and sanding a better circular section. They also make great CA glue applicators

If you want to get real crazy, you can take your razor saw to it and cut out square sections, like you wood (pun intended) with a tree

I myself never really used sprue for antennae or anything else for a long time, i would just build things out of the box. That is until i ran in to a 1/350 scale Yamato from Tamiya. now i swear by stretched sprue, it definetly takes practice thats for sure to get it just right, but its worth it in the end.

For antennae on armor, I've recently discoverd 54 gauge guitar string. Perfect scale and it's easier to work with (IMHO). Just a thought...

how did you quench it???

One of the big problems I encountered was the sprue warping once it cooled. You can eliminate this by having a water source close by. After heating and stretching, keep tension on the sprue (nice and straight), then quench it immediately in cool water. Even the thinnest strand will hold true and straight.

Steve

HEY,
I was right on the nose? Cool, thats gotta be one of the first times.lol

Randy

Once again you are right on the nose brother Dubix....

I take the sprue, about 2 or 3 or so inches above the flame... rotate until it JUST becomes soft and begin stretching... repeat if necessary, once I am about 1/2 the way to where I want to be, 1/4 if I want it really thin. I pull off the flame and wait a sec till it hardens... then I lower it back down and start again... sometimes it takes several heatings to get it just right. if you try to stretch it all the way at once it probably will sag or melt.

If it catches fire I found baking soda works to put it out.,.. (haha kidding)

Actually melting just the tip of one till it is almost boiling then sticking it on the origin then QUICKLY the end of where an antenna is supposed to go makes a mighty fine antenna for an aircraft... most string is too big, even sewing string... for the smaller scales anyway...

HEY,
One thing ive learned is if you want really thin stuff, stretch it a bit when you just take it out of the flame, then let it harden for only a second or so, then start stretching it again. Dont nkow why this helps, but ive noticed that it doesnt break as easily and you can get it thinner.

Randy

yeah I remember when my dad was modelling way back when I would watch him stretch sprue for armor antennas, stretch it REAL thin for aircraft antenna wire. (even 1/72!) etc... I dont use it much but now and then it comes in handy in a bind. I've even done it to approximately the size of a strut or such thing then sand/carve it down to replace the original.

Best thing to do is what Mike V said, but just take scrap pieces and practice at it awhile learning how slow produces how thick etc. And how far you can actually stretch it before it separates. I found when I first did it I would get frustrated if I couldn't get the desired result after two or 3 times. After playing with an entire sprue set I finally got it down...

HEY,
It is easier to buy it, but if your like me and try to save money wherever you can(some people call it being cheap, but i just say they are jealous that i can do it and they cant), you can do stretched sprue. Its easy once you practice some. You just have to make sure not to pull to fast or heat it too much or it will break.

Randy

Hold it over a candle about 2-3" away until it starts to soften.
Then move it away from the candle and pull it.
The speed you pull it determines how big around it is and it takes some practice.
I think it is much easier to just buy some round stock plastic from Evergreen and don't go through the trouble of stretching it.

Mike