Candle bridge

[Marsha]

When you buy a mold there should be instructions included like how long to make the glass.  I traced the bottom and after it was fused it was shorter on one end than the other. And it rocks back and forth slightly.  I also glued the stripes on and one of the purple ones went crazy and squiggled...what caused that????  Should I be using my side elements instead of the lid ones???

[Kev]

In measuring you have to take into account the curve of the mold, so what you want to actually want to do is measure across the top of the mold from end to end to get the size of glass needed. This will incorporate the extra length needed because of the curve.

[Marsha]

Thanks!!  I should have known that!!!!

[Kev]

We all have our moments...LOL

[Anne]

I did the same thing with my first candle bridge too Marsha! One of my senior moments I thought - glad to hear I'm not the only one lol.

[ct4mom]

I so glad you posted this Marsha, I just got a candle bridge mold and I would have done the same thing....lol Gotta love our senior moments!!!

[Kev]

..they do creep up on us..more frequently than we would like.

[Stephen Richard]

Well, and not surprising given my track record, I disagree about candle moulds.  They are are one of the most difficult moulds to use. You are doing an combination slump and drape.  You slump into the middle and drape over the sides. 
Lets get the strips out of the way first.  If you want straight lines from strips or stringers or rods, fuse the piece flat first so nothing can roll about as the glass forms to the mould.  Trying to slump and fuse at the same time will give the kind of problems you had.  It also reduces the life of the mould.
The candle mould requires the glass to fall into a small opening, this requires long soak times. Long soak times mean the glass that is draping stretches while the central portion is trying to fall into the opening.  Of course, if you don't want the depression to be flat, you don't have to soak so long and the effects on the draping part of the of the glass won't be so great.
I have never been able to get a stable candle mould whether 3mm or 6mm.  I always have to grind the base a little to be stable.  I take it as part of the process.  My soak is 90 minutes at my process temperature.  This gives me a flat depressed area for the candle to sit, but it also means that the draping glass has been stretching.  Therefore, I do just measure the width of the mould and make my glass that width.  There is enough height in the moulds I have used that it does not make any functional difference if the glass does not reach the bottom of the curve on the mould.  It is better than hanging off the edge.
However I have also found that cutting the glass to follow the curve at the ends of the candle moulds leads to problems, so I cut mine square and round the corners before fusing.  You also need to remember most moulds are made with a draft so that if glass were to fall over the edge that it will still be possible to get the glass off.  The draft means the diameter of a circular mould is greater at the base than it is at the rim.
I am not positive what is meant by being "shorter on one end that the other and it rocks".  However, anything than exact square positioning of the glass on the mould at the outset will lead to a parallelogram which will not be stable.  Any movement while it is in the kiln will also cause that.  The result is a rocking/unstable piece.
Since the mould is only the base for us to work on, instructions on the size to cut the glass are probably inappropriate.   

[Marsha]

Thank you for all the info Stephen!!  I did make the blank before putting it on the mold.  That's why I can't understand how the line got so squiggly!  I even glued them down.  When I first saw it in the kiln, one side of the glass went to the bottom and the other was a couple inches short of it. Glad to hear I am not the only one having trouble with that mold!!

Here's a few more new ones......Any help or comments?

[Kev]

I would suspect with the first one the raised partition in the center is going to shorten up the piece. So...how can you do this one...I'm curious as well.

If you add the heights of the partition x2 to the length, then I would suspect the base glass initially would overhang the mold and run the risk of folding over the outside edge and catching on the mold with the slump.

[Kev]

Marsha...was your candle bridge base 2 layers thick?

[Marsha]

Marsha...was your candle bridge base 2 layers thick?

Yes, two layers of black.  One stinger and two noodles glued on with hairspray.

[Kev]

OK..I was thinking if it was only one layer that that might account for it pulling in.

[Stephen Richard]

I think you misunderstood me - or I am misunderstanding you.
I meant that if you had full fused the blank before putting it on the mould, you would have known whether the lines were straight or not.  Glue is only useful to put the item in the kiln.  It burns off long before the glass becomes sticky.  In some cases, too much glue can make the problem of moving pieces worse if the glue boils off.
Your description of the result of the slump make me think the piece was not centred on the mould - or it moved during the firing.  Secondly, it may be you are firing too hot if one side stretched to the bottom.

[Stephen Richard]

I would suspect with the first one the raised partition in the center is going to shorten up the piece. So...how can you do this one...I'm curious as well.

If you add the heights of the partition x2 to the length, then I would suspect the base glass initially would overhang the mold and run the risk of folding over the outside edge and catching on the mold with the slump.

Well, as you now Kev, I don't think such calculations help all that much.  The glass stretches into the moulds with low temps and long soaks. 
I agree if the glass were cut to your method, the mould would not be useful.  In fact, I would not be using any of these three without a lot of supporting structure around the moulds.

[Kev]

Wouldn't you have had to fuse the base together before slumping? Were the stripes put on at the same time the base was fused together? Now I'm confused...lol

[Kev]

So in regards to the partitioned mold, the 2 layers of glass as the base gives the piece enough volume to stretch down into the wells of the dish without pulling in the sides..correct?

What kind of support do you mean Stephen?