Metal Casting Zone

Hello everybody. Man this stuff is addictive I have hardly been able to think about anything else the last week.

I am a sculptor and inventor in Pacific Northwest of the USA. My molding skills are in casting clear and colored polyurethane resins in platinum based silicone. (Pressure casting both molds and objects at 35 psi.) I'm not too shabby in this but as I was running out of everything at the same time I decided to explore casting white metals in the new silicones I am choosing.

So after setting up a new Lee Melting Pot(10-lb)on a large ceramic tile atop my kitchen stove I started making a mess. I had bought what was supposed to be a lead free alloy, Tin 92%, Antimony 7% & Silver 1%. But after over heating it repeatedly I ended up with 1/3 pound dark red mater I suspect is copper, so who knows what was really in it. I did manage to polish up some silver looking hummingbirds. Glad I had the stove vent going full tilt.

So my new plan is buying direct from manufacturers, mostly from Hallmark metals. They have a doable eBay volume listing and replied repeatedly to my email queries. Likely I will also sample some from www.rotometals.com as well.

In particular from Hallmark:
MPK 98.5-Tin, 1%-Bismuth, 0.25-Copper, 0.25 Silver.
92-8 92%-Tin, 7.75-Antimony, 0.25-Copper.
Suggested easier to cast than alloys with 1% copper.
www.ebay.com/ Search item # 200428350147
www.hallmarkmetals.net/index.htm

I would love any feedback on these materials.
Also any suggestion on Smooth-On or other non-organic silicones used to cast these types of metals. I will likely want to gravity cast with lots of fine air sprues and doubled volume pour overhead to force metal into details. At least that is my notion at present.

End application is finished jewelry in MPK and anatomical element prototype castings in 92-8. I am thinking that 92-8 might be superior and easier to achieve fine details for jewelry items to be electroplated gold and patinas as well as less expensive.

Yet another item I need advise about is a thermometer. The non-contact infrared thermometer in the following listing has overwhelming good reviews as well as averages temp and current temp, -76 to 932 °F (-60 to 500 °C). I will be working below 650F
www.amazon.com/IRT0421-Non-Contact-Infrared-Thermometer-Targeting/dp/B0017L9Q9C/ref=sr_1_5?ie=UTF8&s=hi&qid=1263776191&sr=1-5
Do these non-contact infrared thermometers work with molten white metal in a Lee Pot? Any of you using these now?

OK next question, is about powdering the mold. Using the soft 25A rubber molds I had on hand worked for a couple pours and then became tack and lost detail. After some searching about I found talc and graphite was suggested. dollar store talc didn't help, so I next ground up some pencel refills. Seemed to help. Then I bought some lock lubricant that is mostly powdered fine graphite and another ingredient that is NOT safe to breath so I was cautious. I then got 6 castings with no degridation of the mold and the graphite seemd to still all be in place. When I talked with Bruce at Contenti this morning he said most of his people use mica for mold layer seperation and talc inside the cavity and or on objects to be cast. He said they put the talc in a sock and slap it against the mold and then clap the mold sections to shake out the extra and then proceed. I am needing smooth surfaces and highest detail possible and of course the most complete fills. Any suggestions?

Also about tubing castings with ceramic media and a professional detergent; would one expect to be able to skip polishing & or burnishing by this process?

Well I better shut up and listen now....

Stephen

Do they offer any flux for the pewters? I have flux for printers lead that helps keep the dross down and cleans up the metal so it flows better and comes out pretty shiny. It's like a soldering flux but it comes in a wax and lanolin brick.
It works but makes a lot of smoke.

Jammer,
This description likely answers your question. But if you click on the image of the product in the following link you will find that the use and cautions are mostly readable. The mention of a perforated ladle was new to me. I had not seen these listed as yet bit drilling chamfered holes (beveling the edges of the holes) in a stainless steel ladle wouldn't be difficult. Do read the caution section as the gas will have to be vented and an duel filtered face mask would likely be a good idea, about $50. Also a small flame up and smoke is a normal part of the process as I understand it. The real value in these extra steps I would imagine is for those of us seeking very high detail requiring very little impurities. As always read the MSDS before purchasing and prior to use, vendors by law must provide them pre and post sale.

Salammoniac Flux
"This flux is a cleansing agent used to remove impurities from molten tin, lead, and zinc alloys. Provided in a pail of 5 lbs."
www.contenti.com/products/spin-casting/176-084.html

I have a dual filter mask and do most of my pouring in my garage with the doors open. I have a type casting machine that I cast lines of type on for printing, I use some flux in that to keep the mouthpiece clean.

I didn't know they still called it Sal Ammoniac. When I ask for that I get weird looks.
Then I say Ammonium Cloride and they know what I mean, but still don't carry it.
I got a good supply from a printer friend.

You live just outside Tacoma? I used to live in Seattle and then in Auburn. Did a few jobs in Olympia and in your area. I miss the northwest. I'm back in Ohio, where I grew up.

Yep, in fact just a few blocks south of Tacoma in University Place. The cloud cover can be gloomy here but it suits me. I like the ethnic mix we have here, adds texture to the melting pot. Only drove threw Ohio when young, pretty uneventful as I remember.

I called RioGrande and talked with them about a few of these issues, but didn't mention flux. It does seem the material is useful to you. And might forstal some poosity in the fine figures I will be casting.

The RioGrande tech was struggling pretty hard to answer my questions but came up short on most of it, but honest and exacting in what he did know. It is all just so specialized. Only folk like me just starting probably fuss so much about the details of getting it done. They thought the infrared non-contact thermometer sounded great but hadn't tried it. The tech did point out that I would be getting the temp at the surface of the melt and not near the spout. I was thinking if I hit dross I would get a different figure too. But no matter - it is worth a go, especially since it will not get it dirty and I suppose I could return it.

So are you publishing a local weekly?

Since your dealing with low temp melts, some thing like this pyrometer might work for you. I use something like this in my lead pot. IR thermometers are great but do have problems getting an accurate reading sometimes. They can focus on the hot air above the melt or mis-read temps because of reflection off of shiney metal.

Edit:
Well, it doesn't look like the link is going to show up. Go to E-bay and look up...

Atkins Hand Pyrometer.. $25



No, I don't do a weekly publication. Letterpress printing is another hobby I don't have time for.

Holy Cow Jammer! That looks great and made in the USA for $25!

I'm using a Lee IV 10 pound melter. I won't be going over 650F.
The listing says:
0' to 1300' F Intermittent, 0' F to 750' F Continuous

I am wondering if the leed would melt if I left the probe in. I might also wire a 9v adapter to the gizmo. $31 with shipping. I'll down load a manual from them if available. And perhaps give them a call.

EDIT: Cooper bought Atkins in 2001 so these inexpensive units are old stock and likely very goo deals. I'll pick one up. And when I can't resist the temptation any longer later buy an infrared. I'm curious if Annie's temp goes up when I piss her off, usually once a day.

This is very good info Jammer. I just had a hunch the infrared wouldn't work. reflections and such as you mentioned.

Bye the way I am the king of starting hobbies I do not have time for. But collecting new skills sure is a lot of fun. I remember visiting the printing areas of a local newspaper while young. It all seemed so magical yet so very sensible.

Links for the curious:
www.cooperinstrument.com/Thermocouples.asp#6
www.maaseh.com/cgi/search.pl?S=atkins&C=50974

My linecaster is a gas pot. I have an old analog pyrometer in it all the time. Printers lead melts around 540 F and casts best at 565 F. Once it reaches temp I adjust the gas so it holds there. The old mercury bulb thing that is supposed to adjust the gas automatically, quit working a couple years ago. This machine was built in 1926 so I think the warrenty is up. I didn't know it had quit until I was casting hollow type and molten lead was spilling from under the machine. I believe it damaged my lead by causeing much of the Tin to oxidize out. I could get a good cast and ended up draining the pot and putting new metal in. I had about 50# to make sinkers out of.

I suppose if you get pewter too hot it will change it's casting properties. It's too expensive to make sinkers out of.

I just bought some Bismuth, it's fun to play with. Trying to grow some crystals. I got a couple small ones but nothing bigger than 1/2".

Jammer:
"I suppose if you get pewter too hot it will change it's casting properties. It's too expensive to make sinkers out of."

That it does I will try to attach three images of my last experiment.

This was one pound of white metal supposedly 92% tin, 7% antimony and 1%silver. (( minus a two ounce hummingbird iI already gave away. ))

I will not quote the vendor as I bought it a year ago and perhaps I am incorrect about the source. Using this Lee IV 10 pound pot without a thermometer I tried casting into a few 25A durometer Smooth-On Rebound 25 Molds at about setting 6. Some bubbles and little dross. Dropped to 5 and it would not pour. Tried 8 9suspect way too hot maybe 800 F. And the material rapidly separated into black powder and the red matter you see in the images. I then tried dollar store talc to rid myself of the bubbles I was getting on the surface. All the while loosing material now even though I had worked my way back down to 7 and then 6.

I did some Google searches and found an old timer that uses powdered graphite on all his silicon pours. Being 2AM all I had on hand was some mechanical pencil leads (graphite) so I ground them up and rubbed them into the mold. Worked pretty good. More research the next day and decided to to pop down to the local auto shop and bout some lock lubricant. (Mostly graphite but other things you would not want to breath so care was taken and only used a couple times.) After dusting this stuff in I got remarkable detail, far from perfect but much better and the degradation of the molds with each pour had stopped. I was only getting 2 pours before the rubber surface turned into jelly. With the graphite the molds showed no damage after six pours. SO pure micro-fine graphite will be purchased along with more pewter and a thermometer next month.

Image two of three.

Here you see the initial set up. It will be improved. I am working with zero lead and cadmium, period. Doubtful of this last alloy so buying directly from the manufacturers from now on. Hallmarks materials most likely. That is a 24" (60cm) floor tile atop of aluminum foil, atop of an unplugged kitchen oven directly under the oven fan driven vent. The red and peach rubbers are all Rebound 25.