F.C. Gold Casting

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When casting my F.C. golds, Ive been getting small pits..usually on the surface, so they can be rubber wheeled and polished out..but they shouldnt be there. Generally near the location of sprue attachment, but can be scattered elsewhere. Im familiar with casting porosity and im quite sure this isnt the case. I believe Im using clean wax (although Im leaning to be suspicious that this might be the problem),investing with whip mix beauty cast, burning out multi-stage with final temp at 1175-1200 F*. 1.5 turns on a kerr centrifico broken arm casting machine, clay crucible, propane-oxy, multi orafice tip that I take off and clean inside daily. Alloy is Jensen JYE: 52 Au, 24 Ag, 18 Cu, 5 Pd. It has also happened in my econo silver alloy, invested with microstar, 1300 F*. :confused:
 
TheLabGuy

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Can you take a picture of your sprue (or lack of) for us, including the reservoir please.......
 
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I cant at the moment...Ive been using Ivoclar-Williams triwax large direct. Its an 8ga. feeding into a 7mm reservoir. The feeder I keep at +- 4mm so the res. stays in the middle of the ring, and attach to the thickest part of the pattern, and use 12ga. chill vents. I always taper the reservoir towards the pattern to try to avoid turbulence in the metal. I changed hoses on the torch to a grade "t" because when this problem started I thought the inside of the old hose from the propane might be breaking down.
 
dmonwaxa

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My guess its either two things:
1.Investment breakdown, from high heat for too longh a hold time or if sprue former and spruing is rough, then when molten alloy enters the mold the sharp pieces may break off and become dispersed in the casting.
2. Gassing or super heating, when the alloy is being molten compressed air or oxygen may become incuded in the melt if the torch is improperly adjusted.
 
TheLabGuy

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These are my two guesses........only because I've done it a few times.
1. You are not following your specific gravity (density) when you cast. You should be weighing your sprued wax ups, then times that by the density and that is your exact weight you should be using, and only that much.
2. Now if you still notice you get them, it's usually because it's a big crown, larger crowns you should use some chill vents.

Now, if you go back to some older threads, you will see that I posted some pictures and we all had a long conversation about this previously.....i'll try to find the thread.
 
DMC

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I'm not too happy with the quality of Gold from Argen the past nine months or so. Seems to have tons of copper and aluminum in it?? Am I crazy?
 
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I do weigh my patterns and sprue and dont get any button beyond my reservoir except maybe a mm of feeder, and Im thinking not investment break-down because its been happening on the whites too and I use microstar on those. Im thinking theres a major clue in that the pits are on the exterior surface and dont permiatthe casting. Do you guys clean your torch tips? When I take it off, I rap it on the counter onto a piece of white paper, and get dark dusty flakes. Im not sure if its shedding from the copper tip itself of a carbon residue maybe? -but theres no burning going on inside the tip...?
 
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I Looked closely under the microscope and the voids arent round like a gas or air bubble, theyre irregular, and one spotwhen I was polishing seemed to be an almost microscopic protrusion that became more evident as i polished to the point I could feel a snag if I lightly slid a sharp bard-parker into it. Im going to do another gold tomorrow...Ill start with new wax, clean the tray in my burnout oven...???
 
sixonice

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When casting my F.C. golds, Ive been getting small pits..usually on the surface, so they can be rubber wheeled and polished out..but they shouldnt be there. Generally near the location of sprue attachment, but can be scattered elsewhere. Im familiar with casting porosity and im quite sure this isnt the case. I believe Im using clean wax (although Im leaning to be suspicious that this might be the problem),investing with whip mix beauty cast, burning out multi-stage with final temp at 1175-1200 F*. 1.5 turns on a kerr centrifico broken arm casting machine, clay crucible, propane-oxy, multi orafice tip that I take off and clean inside daily. Alloy is Jensen JYE: 52 Au, 24 Ag, 18 Cu, 5 Pd. It has also happened in my econo silver alloy, invested with microstar, 1300 F*. :confused:

in my opinion, your burnout temperature is too high for these full cast alloys, especially if the beauty cast is a low temperature investment (which I think it is??) if this is the case you should be burning out at 900-1000F. now if the beauty cast is a high heat investment, i would burn out to the manufacturers instructions, then 30 min prior to casting I would still turn down the temp to 950 or 1000F then cast. sounds like your mold is too hot.
 
doug

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I'll agree with Sixonice. We've used Beauty Cast for years and max temp is 1050F
 
Wyolab

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I was having similar problems a few years ago. I agree with everyone who says lower your burnout temp. This is an easy place to start. I had a combination of a worn spring in my casting arm, combined with too high burnout temps. I had a hard time narrowing it down until I talked to another technician. What a great resource this website is.
 
CatamountRob

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This is what I do, I sprue with an 8 Ga. direct sprues to the thickest part, Burn it out in 2 stages to 1200 degrees, move it to my other furnace which has been preheated to 975, leave it there for 30 min. and cast w/3 turns on the casting machine. If some portion of your crown is larger in cross section than the ball on the 8 ga. sprue, add wax and bulk up the ball. I used to have porosity once in a while, but never since ive used this method. Good luck, Rob
 
JohnWilson

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I'm not too happy with the quality of Gold from Argen the past nine months or so. Seems to have tons of copper and aluminum in it?? Am I crazy?

We use exclusively Agren alloys and have seen consistent product from them. We use 3 different Type 3 gold from them and everyone preforms flawlessly.

I would imagine the OP is just overlooking something very simple. A picture of his button will be very informative.
 
dmonwaxa

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We use exclusively Agren alloys and have seen consistent product from them. We use 3 different Type 3 gold from them and everyone preforms flawlessly.

I would imagine the OP is just overlooking something very simple. A picture of his button will be very informative.

I have to agree with John, I have been using Argen for years and never have had a single problem with their products.

Some advice for the new guys; if you have a situation, don't hesitate to call the product manufacturer. Their number is usually on the product label, and their website can be very resourceful.
 
TheLabGuy

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Some advice for the new guys; if you have a situation, don't hesitate to call the product manufacturer. Their number is usually on the product label, and their website can be very resourceful.

I wholeheartedly agree, I can't tell you how many times I talked some smack about a vendor only to realize it was my own dumba$$ fault because I didn't take the time to look the information up or read the manual like it said in bold enlarged print most of the time. As for Argen, I love them, I'd be hard pressed to go elsewhere, my rep. (Alberta) is awesome!!!!!!!
 
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I'm betting on hot heat.

What are the setting on your oxy/prop........bet its to hot.
Use the burnout temp thats on your alloy direction....... yours seems high.
Seems like I used 900 temp with beauty cast years ago with a room temp bowl of water.....yes I did !! for many years.......s m o o t h castings !
I now use 1200 temp with Microstar HS with Ivoclar Midi gold 50... 45 minutes and cast........
Use 2 winds even though this may not have any bearing..... less is better if you aren't seeing miscasts. I use 2.5 or 3 turns on type 3, and 4 turns on Noble ceramic... with the Kerr machine.
Don't burn out for hours and hours, may receive rough casting. 45 to 60 minutes is fine for one ring....

I use 8ga reservoir sprues on the thickest cusp, usually the lingual.....On really heavy-large molars, use two sprues...... I even use 6g reservoir sometimes.

Where you attach your sprue, flare out the sticky wax around your pattern. Years ago I would rarely see porosity and or small pits near the sprue and or other places, this solved the problem!

Charles
 
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dmonwaxa

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My gosh Charles, there must be an echo in here or this is dejavu. Someone who finally side with me. Yes burnout is at 900 when using the "hygroscopic" technique to achieve expansion, I believe it was 100F or 105F at 45 mins. if my memory serves me right. High heat technique; Hi temp 1200F. Since Beautycast is a gypsum based investment it does not hold up well to prolonged high temps unlike phosphate bonded type investments. Like you, I think the temp of the melt should be of concern since oxygen is being used. Oxygen of high burn out temp and high melting temp causes the metal to boil per se in the mold. The outer surface solidifies and the internal bulk of the metal remains molten which causes unusal strain in the matrix resulting in voids in the casting. Now the extent to which this happens is depedent on two variables; time and temp. Can I get an amen.
 
TheLabGuy

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I thought it was hydroscopic, hence the water used? I use to do the hydroscopic method in-house back in the day on all my post&cores because the patient was in the chair waiting, worked good. Used it for full cast too but preferred to let it bench set the full time, felt I got better expansion rate is all.
 

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