First Time Casting
Posted: Sat Dec 05, 2020 9:51 am
Hey guys, sorry for the noob questions, I bought a second-hand vacuum casting setup during lockdown (per cast vacuum caster, kiln, furnace etc), it’s my first time casting, never been taught, in my apprenticeship my boss used casting houses and I don’t know anyone else who does their own casting, nor 3D printing here (Melbourne, Australia) You guys in the US and Europe seem to be much more advanced jewellers than us Aussies with these sorts of things.
I have tried 4 casts and they have all been pretty terrible.
First flask blew out the bottom when pouring (I think I didn’t have enough plaster over the model), the second had parts which the metal didn’t fully congeal so I upped the metal temp the next turn.
Third was white gold one (pictured), fourth was red/white looking ring (pictured)
There were no casting books in stock here in Australia so I read the Stuller guide and checklists for investing/casting, watched every youtube video I could find, and I’ve read a lot of posts in this casting section of the forum (most after trying I admit) and I’m guessing my major problem is either investment breakdown or maybe ash problems, but I’m not sure and was hoping someone could nudge me in the right direction.
These are the main details:
Investment: Goldstar Omega+, mixed at 40:100 ratio using kitchen mixer, vacuumed, invested in flask, vacuumed, left for 90mins before going into a cold kiln.
(Omega+ was the only investment powder in stock here designed for casting resins)
Resin: Easycast HD Brown. Models were perfect
Flask size: 85mm x 100mm height perforated
Burnout: Exactly as instructed by Goldstar Omega+ (below)
I mix the investment with a kitchen mixer in a rubber bowl, vacuum, pour into flask, vacuum flask, sit for 90mins then into cold kiln and start program.
The red/white looking ring with heart shaped setting was actually newly alloyed 9ct yellow gold 37.5% pure gold granules, 31.25% copper, 31.25% silver out of the acid, and the other was 18ct white gold using clients old gold.
(Red I believe is from ferrous metals but no idea what makes parts go white/silver plate)
I don’t think it’s vacuum, as both sides of the machine reach full vacuum in 5-10 seconds, and after I turn the pump off after a cast, it holds vacuum for long time unless I lever the flask out of the machine.
I don’t think it’s curing, as my casting house gets flawless results in silver, gold and platinum on my current curing routine. I also get pretty shitty results when I’ve given them an under cured part which makes me think they don’t do any further curing on their end. (pictured below)
My curing: Direct Australian sun on rotating platform for at least a few hours - usually the whole day, or if it’s heavy overcast, under strong hydro grow lights for at least 6+ hours. (I will now add 5 x 5min microwave water boil technique)
My guesses:
The setup came with an old Italian smelting furnace, which died after once use lol, so I’ve been using a torch – which I could be pouring the metal in too hot causing investment breakdown?
Is there a trick to getting the right temperature with a torch while I wait for a new furnace to arrive in the mail?
Could it be ash or airflow? I’ve noticed a lot of people here vacuum their flasks, flip them or find ways to add more airflow in their kiln (wish I read that first).
I just have a duct from the top plug hole going straight outside, and I have been sitting the flasks on a cake warmer on a pizza tray, which I noticed has slumped under the heat
Should I remove the front plug off the door for more airflow?
Spruing? I’ve never done it before but I did make sure the joins were smooth to assist flow. I used the large sprue for the first 3 and sort of carved the top like an arrow it so it flowed into the ring width.
I have noticed some people here use multiple sprues rather than just the one main one, but then a lot of you don’t – both with great results so I’m not sure how critical this is.
I only used one as my casting house only ever uses one, with great results, plus I read some things about creating turbulence if you don’t do the multiples correctly
Any tips to troubleshoot would be much appreciated
I have tried 4 casts and they have all been pretty terrible.
First flask blew out the bottom when pouring (I think I didn’t have enough plaster over the model), the second had parts which the metal didn’t fully congeal so I upped the metal temp the next turn.
Third was white gold one (pictured), fourth was red/white looking ring (pictured)
There were no casting books in stock here in Australia so I read the Stuller guide and checklists for investing/casting, watched every youtube video I could find, and I’ve read a lot of posts in this casting section of the forum (most after trying I admit) and I’m guessing my major problem is either investment breakdown or maybe ash problems, but I’m not sure and was hoping someone could nudge me in the right direction.
These are the main details:
Investment: Goldstar Omega+, mixed at 40:100 ratio using kitchen mixer, vacuumed, invested in flask, vacuumed, left for 90mins before going into a cold kiln.
(Omega+ was the only investment powder in stock here designed for casting resins)
Resin: Easycast HD Brown. Models were perfect
Flask size: 85mm x 100mm height perforated
Burnout: Exactly as instructed by Goldstar Omega+ (below)
I mix the investment with a kitchen mixer in a rubber bowl, vacuum, pour into flask, vacuum flask, sit for 90mins then into cold kiln and start program.
The red/white looking ring with heart shaped setting was actually newly alloyed 9ct yellow gold 37.5% pure gold granules, 31.25% copper, 31.25% silver out of the acid, and the other was 18ct white gold using clients old gold.
(Red I believe is from ferrous metals but no idea what makes parts go white/silver plate)
I don’t think it’s vacuum, as both sides of the machine reach full vacuum in 5-10 seconds, and after I turn the pump off after a cast, it holds vacuum for long time unless I lever the flask out of the machine.
I don’t think it’s curing, as my casting house gets flawless results in silver, gold and platinum on my current curing routine. I also get pretty shitty results when I’ve given them an under cured part which makes me think they don’t do any further curing on their end. (pictured below)
My curing: Direct Australian sun on rotating platform for at least a few hours - usually the whole day, or if it’s heavy overcast, under strong hydro grow lights for at least 6+ hours. (I will now add 5 x 5min microwave water boil technique)
My guesses:
The setup came with an old Italian smelting furnace, which died after once use lol, so I’ve been using a torch – which I could be pouring the metal in too hot causing investment breakdown?
Is there a trick to getting the right temperature with a torch while I wait for a new furnace to arrive in the mail?
Could it be ash or airflow? I’ve noticed a lot of people here vacuum their flasks, flip them or find ways to add more airflow in their kiln (wish I read that first).
I just have a duct from the top plug hole going straight outside, and I have been sitting the flasks on a cake warmer on a pizza tray, which I noticed has slumped under the heat
Should I remove the front plug off the door for more airflow?
Spruing? I’ve never done it before but I did make sure the joins were smooth to assist flow. I used the large sprue for the first 3 and sort of carved the top like an arrow it so it flowed into the ring width.
I have noticed some people here use multiple sprues rather than just the one main one, but then a lot of you don’t – both with great results so I’m not sure how critical this is.
I only used one as my casting house only ever uses one, with great results, plus I read some things about creating turbulence if you don’t do the multiples correctly
Any tips to troubleshoot would be much appreciated