prefiring a mould?

Started by shafeenan, October 03, 2015, 12:57:00 PM

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shafeenan

At vast expense (to me anyway) I have just bought my first mould and coated it with primer. Do I fire it before using it like one does with a shelf? In which case, to what temperature?
Many thanks - don't want a lovely new mould with glass stuck in it on the first firing!

Nicknack

I've never prefired a mould, and I've never had any trouble.  Just make sure you've coated it 4 times (once in each direction) and fire away.

Nick

Zeldazog

With my first moulds, there was instructions in the box to fire the mould first anyway - I can't remember how hot, I just remember that it was slowly.  Take a look on Creative Glass or Warm Glass and see if there are any advice notes or instructions


marklaird

I don't pre-fire mine either and have not had any issues. I don't think I've ever had to recoat the shelf primer either even on ones that are used regularly. Maybe I'm just lucky.

Zeldazog

Quote from: marklaird on October 06, 2015, 12:25:14 PM
I don't think I've ever had to recoat the shelf primer either even on ones that are used regularly. Maybe I'm just lucky.

I think it says on the data sheets on Creative Glass Shop/Guild )whichever it is that's linked the the mould maker, Creative Ceramics) that if you don't fire above 720 degrees, you shouldn't need to re-coat unless it's degraded.

I think it was there that I also read about pre-firing, but it just said for larger moulds. 

flame n fuse

The prefiring may be a safety precaution to ensure the mould is dry. You do need to recoat them occasionally - when it flakes, but not necessary every time.

ajda

Quote from: flame n fuse on October 06, 2015, 06:37:48 PM
The prefiring may be a safety precaution to ensure the mould is dry.
I think the drying out is the most important thing - I've cracked moulds by not drying them out thoroughly before use. I coat with kiln wash, allow to air dry for a good long time, then fire at 200C for a couple of hours to drive out any moisture trapped inside the clay - though you can do that as the first stage of a fusing/slumping cycle.
Alan
www.ajdalampwork.etsy.com

shafeenan

Don't seem to be very good at finding my way to and from posts - I could actually spend all day on this site just finding things I didn't know about!  Ha! so -  finally I must say THANK YOU to the answer to my query about firing moulds.  i am going to cross my fingers and give it a go today withougt pre-firing and hope for the best.

Rascal

Good luck, have had my first successful slump and was so pleased when I didn't break the mound or glass. Just found my original leaflet which came with the mould and it does say no pre firing necessary unless mould is over 30cm. Look forward to seeing the end result.