stupid glass blowing question....

[Alison D]

I am blowing some soft glass ornaments off the end of a hollow mandrel. Things are going well and I am very pleased with my progress thanks to all of the help everyone has provided.

My question is... Can I make a 2 part plaster mold to blow into or will it just burn up? I am looking for a cheap way to make molds to blow the ornaments into. I really wanted some Easter eggs and couldn't come up with a way to do it in time.

Happy Easter to all those who celebrate, and thanks for all of the continuing aid and support you show for all of us learning without the aid of classes.


Alison

[ArtcoInc]

I am blowing some soft glass ornaments off the end of a hollow mandrel. Things are going well and I am very pleased with my progress thanks to all of the help everyone has provided.

My question is... Can I make a 2 part plaster mold to blow into or will it just burn up? I am looking for a cheap way to make molds to blow the ornaments into. I really wanted some Easter eggs and couldn't come up with a way to do it in time.

Alison

Yes. Use a 50/50 mixture of casting plaster and silica (200 mesh). The mold won't last *too* long, but it will work. Make sure it is completely dry before you use it.

Malcolm

[Mike Glass]

Go to the craft store and buy some Hydrol-cal.
It's just like plaster, but it can take the heat. I make vacuum forming plugs with it and I get about 1000 pull from a plug before it shows signs of cracking.
The plastic that I form hits about 600 degrees.

You can also buy the stuff they use to cast slumping moulds. It's sold just like plaster also.

Mike

[scoutycat]

I'm curious why you don't want to just shape it in the flame? Are you worried about uniformity?

[ArtcoInc]

Go to the craft store and buy some Hydrol-cal.
It's just like plaster, but it can take the heat. I make vacuum forming plugs with it and I get about 1000 pull from a plug before it shows signs of cracking.
The plastic that I form hits about 600 degrees.

You can also buy the stuff they use to cast slumping moulds. It's sold just like plaster also.

Mike

I too would use either a Hydrocal/Silica mixture, or an even stronger material like Castalot. But, the OP was asking for cheap.

Malcolm

[menty666]

My guess would be that she wants to be able to do interesting shapes beside round quickly. Make the mold that can hinge open and closed that has some neat shape to it, do the color work on the glass before you insert and blow, bada boom bada blow, got something to show :)

Well, in theory. Tough part for me is always getting the darn things off the point/blowpipe/fused skin.

Hollow cavity blow molds let you do funky shapes, embossed lettering, whatever. I've been meaning to try it myself but I only *just* figured out how the two part molding process works for round things. For some reason I always had trouble wrapping my head around the fact that you sort of build it upside down...so to speak :)

by the way, I'm just guessing but I think if you put it in the kiln for an hour or so at 250 F it might help dry it out if you're impatient.

[ArtcoInc]

by the way, I'm just guessing but I think if you put it in the kiln for an hour or so at 250 F it might help dry it out if you're impatient.

BTW, plaster, like concrete, hardens through a chemical reaction, and not by 'drying'. This is why plaster (and concrete) can harden under water.

(This is also why you *never* pour plaster down your sink or toilet!)

That being said, I have 'dried' plaster in the kiln. I set the kiln to 200°F, though, as I want to stay *below* the boiling point of water.

Malcolm

[menty666]

yeah, popping the bubbles out via steam would be a bad idea :D

[scoutycat]

Well, there you go. I was thinking egg shaped easter eggs - pretty easy to shape, but I guess more intricate ones would be nice. Although, if I went to all that trouble to make a mold I'd want something that lasted a bit I think. Would fiber blanket and rigidizer work well?

[menty666]

It might but the problem becomes how to physically handle it when it's time to do the blow-in. The p/s mix is going to be nice and hard and probably thick enough to not transfer the heat immediately. Plus it's pretty cheap. I think I got a 25 pound bag of plaster and a 25 pound bag of silica for 12.50 each (pottery supply house) whereas I think the ridgizer is a little higher priced in the long run. The only caveat here is that handling the raw materials for the molds is a little riskier since you really want a fine mesh for the silica, which makes it a respiratory hazard and it requires good ventilation AND a P100 respirator. Plus you'll want a scale to measure out the material. But once you've got the hardware and materials, you're good for a while unless you're doing it every day.

Having said that, give it a try and let us know. :D

[Alison D]

Thanks so much everyone. This is what I love about this place. You go to your Dad's house to cook him Easter dinner and you come home and all sorts of generous people have taken the time to help you out. I think I'll try the plaster mix as cheap is unfortunatly a priority. Menty666 hit the nail on the head I have been able to come up with all sorts of wonderfull colors and effects and would love to be able to uniformly form them into something besides rounds.
I am using bead release and shaping the tops like comercial ornaments so I don't need to get them off the mandrel untill after they are annealed.

Malcolm,Would a ceramics supply place carry the silica? BTW, vol.4 is da bomb. I don't know where I will find time to try all these new projects.

Thanks a bunch,
Alison

[menty666]

ceramics supply will have the silica but you may have to ask for it and tell them what you're looking for. It was called something else but I can't remember what.

just tell them you're making high temp plaster silica molds and they'll be able to hook you up.

[Mike Glass]

Making the mould is nothing.
Making the plug is where your going to be spending the most time.
After you have a good plug you can make as many moulds from it as you'd like.

You can start the plug with one of the plastic eggs and add any details you like. Then just cast your mould in two halves. Also very easy to do!

Mike

[Mike Glass]

Also I wouldn't hinge the mould. The swing of the hinge will make it hard or almost impossible to get the mould open without breaking the piece.
Pin the two halves together so the mould opens vertically.

Is vertically even a word???
Mike

[menty666]

I don't know, traditionally two part glass molds are hinged, and it works ok. I saw a wire frame blow in mold once, but even that was hanged, albeit at the bottom.

Alison didn't mention if she was doing soft or boro but the working time isn't really going to be there regardless to try to shift the parts on rails or to try to line up keys. Easiest is just going to be to make the mold parts and hinge it with some duct tape so it opens like a waffle iron. Just make sure you put a piece of wire into the upper half as a handle.

Edit...scratch the waffle iron comment, you'll want to insert and blow from the top so you can use gravity

[scoutycat]

See, that's why I was thinking fiber blanket, you could just fold the thing in half and not rigidize a stripe in the middle for an insta-hinge - and, it's light so easier to handle. But of course I haven't a clue IRL, I've never blown into a handmade mold before. Just marble molds and such.

[Alison D]

I'll have to read up on making a two part mold. I know I have a book with this in it.

I just got a gift certificate to a stained/hot glass shop that carries some fusing and slumping supplies would they have something there to use to make a mold. I have $100 dollars to spend there but I need to save some for glass.
I am blowing 104 and 90 coe glass ornaments if this makes a difference. Gettng enough boro evenly hot on my mni cc for a 3 inch ball is a stretch.

Does the rigidizer last? This sounds doable. This would only work for a basic kind of shape i guess. would you use the rigidizer on the inside and out of the blanket?

Thanks,
Alison

[menty666]

if you remember the way those little "who am I going to marry" finger puppet things the girls did on the playground worked, you'd want it to open kind of like that. Hmm, easier to explain is to picture a V :)

When you make the mold make sure you leave a pathway at the top for your blowtube to enter though, other wise the mold won't close.

[Mike Glass]

That's another good point.
When making the plug you want to make the path for the mandral. You can attach a wooden dowel to the plug to make the path.

Mike

[Mike Glass]

Hey, stop reading my thoughts! hehe

Mike

[menty666]

By the way, if you have a subscription to glassline, check out the article here in their back issues:

http://www.hotglass.com/access/v13n5/clevenger.html

It's an article about making mold-blown ornaments including....how to make a two part blow mold :D

and if you don't have a subscription to glassline, you might want to consider it,it's worth it.

[Alison D]

Check on the mandrel hole.
I don't have a subscription to Glassline. I try not to subject myself to too many new ideas because i keep spending money trying to figure out new things before I even get good at the last new thing to learn.

My dimples would not make a mother proud yet, and I decide to try blowing ornaments,
and the japonese method of making the canes for their florals is calling before I get my first mold made. I am a mess.

You should have a legal release people should have to sign before joining LE.

WARNING!!! Glass work is addictive and may prove detrimental to your bank balance and relationships. PROCEED WITH CAUTION!!!

Thanks again,
Alison