slumping and draping questions

[sweetyetevil]

Hello~ I have been doing some basic glass fusing making pendants and small slump bowls but I need some help on using slumping or draping molds. I have looked all over for answers  online but am not finding anything that is helpful.
I understand slumping- putting the glass into the dish and letting it mold to the shape but how do you know how big to cut the glass before putting it in the mold? What if the mold has shaped edges like a half circle pattern (up and down edges)? How do you shape that?
 Draping- I have seen the draping using flat bottomed items like making a vase but how the heck do you use the molds that are circular or pointed? How do you balance the glass on these?
 Can anyone direct me to any websites or a good book to get to help with these questions? I am ready to move onto other things with glass fusing but I am not quite finding answers for my questions and pictures would be helpful too!
Thanks!

[HSG]

Hi!

Some of your questions are specific to items I'm not familiar with. We have a couple of glass enthusiasts who do just the work you're interested in. They will be able to address your questions specifically.

CrazyEyeGlass, joby560 and TickleTickle would be great to help with these, and more. Hang tight.

[sweetyetevil]

 I hope someone can help...I am so ready to get some new things going but I really am clueless on this!  Thanks!!!!

[HSG]

I will send a PM to CrazyEyeGlass, and see if she can help.

[CrazyEyeGlass]

Sorry for the late reply! I was out of town.
My favorite online resource is glass-fusing-made-easy.com. Here's a link to their bit on molds: http://www.glass-fusing-made-easy.com/molds.html

Slumping:

Some slump molds are more challenging than others and you'll even see them rated in some stores with beginner to expert ratings. Anything that strays from simple geometric shapes, such as the half circle shape you mentioned, will be more challenging.

The easiest way to get the right size and shape of glass for the mold you want to use is to invert the mold onto the glass you want to use and trace the edges of the mold onto the glass with a sharpie (remember to clean the glass before firing). Of course there are other ways to do this, such as simply measuring the mold from tip to tip and cutting the glass to exactly the same measurements. Basically, you do not want any glass to overhang the edges of the mold. If the glass does overhang the mold, you run the risk of trapping the mold in the glass and ruining both your project and the mold. Once the glass is cut and you've done your initial full fuse, recheck the size of the fused glass against the slumping mold--chances are the glass has "shrunk up" a little, but it may be slightly larger after fusing depending on how many layers of glass you've applied. If the glass has shrunk up evenly, no problem! It will still fit within the slumping mold. However, if the fused glass is now larger than the slumping mold, you'll have to repeat the steps above with a sharpie and use a grinder or ring saw to get back to the correct size.

Draping:

Lots trickier than slumping! I don't have a lot of experience with draping, but have done a little (my kiln is fairly shallow, so I can't do any dramatic draping). Draping requires a lot of experimentation. When measuring the draping mold, you want to use a tape measure (whatever tape measure you use--cloth, metal, ruler--do yourself a favor and use the *same* tape measure for your entire project--there are always slight differences between tape measures and if you don't use the same tape measure you will begin to question your sanity) to measure from the surface vertically to the first high point, then up over the top and back down. This will give you the basic measurement; you need to shorten up the measurements when you cut your glass since you don't want the edges of the glass to drape onto the kiln floor/kiln shelf and possibly puddle there. Draping round pieces is easier than draping rectangular or square pieces.

As for balancing, this is very difficult indeed and why it's an advanced technique. You could try placing a small piece of thick fiber paper on the high point to give yourself a slightly more stable area to balance the glass.

If you still have questions about either slumping or draping, let me know and maybe I can gin up some youtube videos in the not too distant future.

[sweetyetevil]

Thanks for the tips! I knew it was going to be much trickier but then I thought maybe there is just something I am missing about the whole thing. I have looked at glass fusing made easy's site but I will go over it more throughly.
I will keep you posted on my trials into glass fusing!

[speedingpullet]

I do both slumping and draping.... maybe I can help?

 - For measuring - I normally measure the mold from edge to edge and subtract about 1/2". As most of my pieces are double/treble thickness, I find a layer spreads just under a 1/4", so taking off a 1/2" ensures the fused piece is not too large that it will overlap the mold.

 - I often have little spurs of glass, or a wavy edge  after fusing. Wet and dry sandpaper or a grinding stone will get rid of little snags and sharp corners - and if you have access to one - a belt sander will make short work of wavy edges.
My rule of thumb is that once its been fused I need to make sure its as smooth and straight as I can make it BEFORE I slump it. Slumping only makes the glass more plastic, and it won't fix sharp edges, etc.

 - Ideally, slump molds should be ceramic and drape molds should be metal (preferably stainless steel). This has to do with the contraction of glass during the heating/cooling process: in a slump the glass will contract away from the ceramic walls, meaning it will cool to be fractionally smaller than the ceramic slump. Whereas a metal drape mold will contract slightly more than the glass on top of it, thereby not crowding out the work on top of it

 - It is possible to use a ceramic drape mold if you remember to create a little space between it and the glass. I normally put a small circle of the thinnest kiln fabric between the base of the glass and drape before the slump fire. This ensures that when the glass contracts it doesn't get stuck on the non-contracting ceramic, thereby cracking the glass as it cools.

 - Slump molds and drape molds require different kiln schedules. For some reason glass for drape molds is much more vulnerable to shock while heating than slump mold glass. 
I've thrown caution to the winds with my slumps and ramped my firing schedule up to As Fast As Possible and still had wonderful results.
This doesn't work with drape molds though! I had to find out the hard way after cracking several pieces that you have to ramp the heat up really slowly. I've had the best results ramping up at somewhere between 150f - 200f per hour to about 1300f and then soaking for 30 mins.

Anyway, I hope this helps! I also found very little information about the difference between the two types of molds, so most things I found out from experience.