How to smooth and polish the inside of 3" PVC Pipe?

I've been asked by our Pastor to cast a 3" x 22" "Christ Candle". I haven't
been able to find a candle mold this big. I have a few feet of new 3" PVC
pipe that I can make into a mold, but the inside is rippled from the
extrusion process. Any suggestions as to the best way to make the inside of
this true and smooth so that the candle can be extracted after molding?
I''ve thought of running a cylinder hone down it, but this will probably not
do exactly what I want, and will leave a grooved surface.
I've thought of buying a piece of 3" copper drain pipe, but this will be
expensive and may be unobtainable in a two-foot lenght. I don't have slip
rollers, so I can't see how I could roll a mold. Any other suggestions?
Thanks for any help or advice you can offer.
--
Bob (Chief Pilot, White Knuckle Airways)
I don't have to like Bush and Cheney (Or Kerry, for that matter) to love
America
Reply to
Bob Chilcoat
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Could you spray it with a thick layer of some kind of release compound?
Best regards, Spehro Pefhany
Reply to
Spehro Pefhany
How about giving it an "Artistic" surface in any of a billion ways. Lots of artists here!
Reply to
Tom Gardner
My advice would be to NOT bother polishing it, but rather look at splitting the pipe, to make it easier to remove it. The wax will have a LARGE surface are to adhere on, and the friction involved in sliding the candle out would be horrific.
I would look at splitting the pipe into at least two pieces, and using hose clamps to hold the mould together during the pour and cooling. If you're worried about the minor ripples etc on the finished candle, you can either dip the entire candle after cooling, or use a plane to smooth it.
The other option would be to use a strip of sheet metal (fairly thin) with enough length to go around the candle at least 2 times. Make a roll around something, and use the hose clamps to hold the rolled metal together. This would make a smaller step" at the seam, and tidier mold release (just undo the hose clapms and roll the candle out of the metal)
my 2 c
Des Bromilow
Reply to
Des Bromilow
Have you tried plastic conduit; I have been told it is smoother.
You could try washing the inside of the pipe with the purple cleaner/activator. If you could manage to apply it very evenly you MIGHT end up with a smoother surface. One possible way would be to roll the pipe in a section of gutter containing an inch or so of solvent.
Reply to
keith bowers
IANA Candle Making Expert, though I have done it a few times. You're going to need some sort of a split mold to get the candle out, it won't just push out of a length of pipe unless it's perfectly smooth and slightly conical, and you have the release agent applied in just the right amount...
One wild idea - Get a 3' length of 4" or 5" snap-lock galvanized dryer vent pipe at the local Home Depot/Lowe's/BORG.
Fold a flange on the snap-lock edges so when the edges are pulled together you have your 3" diameter round mold, it should stay close to round with a little massaging of the metal. Then rig up two stretchers of 1x1 wood for the seam, and a bunch of spring clamps to hold the edges together.
A board and some sheet gasket at the bottom for the base of the mold. A few eye-hooks and bungee cords to hold the cylinder against the bottom. And a big pail, serving tray or steam tray to set it all in, so if you have a big wax spill it's contained.
Thumbtack into the board to hold the bottom end of the wick, pencil balanced across the top of the mold to hold the top end of the wick. Heat and pour your wax, wait a few hours for cooling, then unclamp and slide out the candle.
-->--
Reply to
Bruce L. Bergman
I don't think you are going to have to worry about release. The coefficient of thermal expansion for wax is probably higher than PVC which will leave clearance when it cools and it should fall right out. I would not worry about the ripple. I think you will be able to smooth it by playing a flame or hot air gun over the outside of the candle after it is cast. These are just hunches, I'd try a small one first, may be 3/4" PVC pipe.
Reply to
tomcas
Hi Bob,
... snip ...
After you pour the wax in and let it **thoroughly** cool, run hot water on the outside of the PVC. Should warm up the inner surface of the PVC enough to soften the outer layer of the wax.
Push it out. - Carl
Reply to
Carl Hoffmeyer
Split the pipe lengthwise. Glue it back together with a piece of paper in each of the joints. Cast the candle and re-split the pipe.
--RC
Projects expand to fill the clamps available -- plus 20 percent
Reply to
rcook5
3" stovepipe, don't clip it together, use Duct tape, couple of layers, remove it when cool and clean up the one side, it comes in 24 in length, and you will even have a rippled end to put in the candle holder. My wife has done 12" candles in them, but not, 22". gary
Reply to
Gary Owens
Fiberglass/epoxy or Bondo on a model.
Reply to
Richard J Kinch
Ive seen this done with PVC and Cardboard. Poster board wrapped around a PVC form, with a couple layers of corregated cardboard wrapped around that, snugged up tight with strapping tape. After the candle is cast, simply unwrap it. You MAY have one small mould line on it. Period. All else will be smooth as a babys behind.
Cast the candle with it standing up on a piece of plywood with the cardboard tube well taped to the plywood. Stick in your wick with a weight on the bottom end, centered at the top with a bit of dowel across the top of the form, and as the wax is poured, tap the sides of the tube gently to get any air bubbles flowing upwards. Pour quickly but evenly.
Spraying the inside layer with PAM or other vegitable oils will prevent any tendency for the wax to stick to the poster board.
Gunner
"To be civilized is to restrain the ability to commit mayhem. To be incapable of committing mayhem is not the mark of the civilized, merely the domesticated." - Trefor Thomas
Reply to
Gunner
Nice, although I'm suprised he isn't getting one made professionally or something..?.. Though come to think of it, ours is maybe only 2". I suppose you can't find the extra thickness?
Hrm... not really. I'd be more worried about 1. sticking to the tube and 2. chinking against the bumps.
If you can smooth it out (I invision a gun drill of some sort, or something), that'd be a good way to do it.
Think the bar will be stiff enough to mount in the lathe? That could get it smooth and round.
BTW, as it cools and shrinks, it will shrink *A LOT*. You'll need a pot of plenty hot wax on hand to keep it topped up as it hardens. Once hard, chances are it is much, much more flexible than the stiction to the pipe (even with vaseline or something) that it won't shink at all. A trip to the freezer might help I suppose, but you'll be better off squidging it out with heat on the pipe. At worst you'll need a molten layer for it to slide past everything.
Tim
-- "I've got more trophies than Wayne Gretsky and the Pope combined!" - Homer Simpson Website @
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Reply to
Tim Williams
My Mom used to make these for their church. Use a cardboard tube of the appropriate size then peel it off when it cools. If it needed smoothing then I used my propane torch to smooth it. Karl
Reply to
Karl Vorwerk
I don't have slip
Do a test first to see if you need a split mold. Wax shrinks quite a lot when it cools. Maybe you can finish it on a lathe?
Regards,
Boris Mohar
Got Knock? - see: Viatrack Printed Circuit Designs
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Reply to
Boris Mohar
You might be able to massage the candle out. After you cast it, lay the pipe on the table and roll it back and forth a bit, bearing down somewhat. If you're gentle and the candle is still slightly warm you'll make it a little thinner, but keep it round.
Reply to
B.B.
Split mold will be easier in the long run. Cool VERY slowly and keep feeding wax to compensate for shrinkage . The outside freezes first so they tend to shrink from the ends and can even suck a void from the top as the core freezes up last. You want the whole thing to be at about the crystallization temperature at about the same time which may require warming the mold and holding the whole thing in a warm environment as it cools. Temperature differential from the outside to the core is your enemy.
For a high gloss finish, line your mold with a sheet of mylar. This should be available from many hobby stores. Mylar has one heck of a smooth finish and is also self releasing. We used to use it on resin castings and could peel it off without any release agent, leaving the equivalent of a polished surface without the work.
Koz
Bob Chilcoat wrote:
Reply to
Koz
Split the pipe lengthwise and tape it back together. Spray the inside with PAM cooking spray.
Pour in the wax. Once it has set, seperate the 2 halves.
Reply to
Ernie Leimkuhler
Thanks for all the suggestions. I thought about all of them and was about to set up a steady rest on my wood lathe, and go after the inside with sandpaper on a stick. Then I stopped by a plumbing supplier this morning and just scrounged a piece of 3" schedule 30 pipe, which is much smoother on the inside. The problem I was worrying about wasn't mold release so much as being left with the rippled surface on the finished product. This new pipe is much smoother inside, although it's a bit thin to make a split mold out of. I may glue a strip of the schedule 40 along one side and split it through the strip, although I suspect that the wax will shrink enough that I might be able to push the candle out one end with little trouble. Unfortunately, PVC has a much larger coefficient of thermal expansion than most metals, and may shrink too much with the wax. We'll see.
Anyway, I'll report back after I try my first candle.
Bob
-- Bob (Chief Pilot, White Knuckle Airways)
Reply to
Bob Chilcoat
And if tape isn't strong enough, get some SS Hose clamps and firm up not to tight. Martin
Reply to
Martin H. Eastburn

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