I have been pulling my hair out diagnosing constant issues that popped up the past month or so while casting silver from wax/resin models. I have had 2 years or so of almost flawless castings only for these issues to show up suddenly and relentlessly. I’ve been getting bubbles all over my casts, pitting, and flashing. Not little tiny bubbles…big BLOBS that sometimes completely eclipse details on a ring and the entire thing is scrapped. They are on the sides and tops of models, not under them as you would expect.
I thought to myself, alright, usually bubbles are a vacuum issue, so I leak tested my system - all good. Got a new pump that passes the boil test - check that off…what could it be? I have tried myriad of small changes in the process including boric acid additions, water temperature variation (cold and hot), vacuum time adjustments (more and less), pure wax instead of resin prints, water/powder ratio (moreand less) you name it. I got new boxes of Plasticast and Maxx. NOTHING HAS HAD ANY EFFECT!
Has anyone else using these investments been running into mysterious problems? Is it possible that R&R had a massive bad batch and multiple boxes are no good?
I honestly don’t know what else to try. I’m doing a tree with Optima Prestige soon to see if anything changes.
You’re introducing a lot of chaos by tweaking so many things. Get back control by going back to the basics. Make sure to follow the manufactures instructions. Re-read them until you’re sure you haven’t missed anything. Make sure you have accurate measurements. For timing, weights, vacuum, and both room and liquid temperatures. By doing this you will have eliminated a lot of guessing. You now have a solid foundation to tweak one thing at a time if needed
Some variable has gone unnoticed. Always do a thorough cleaning and rinsing of all equipment and tools used including flasks and bases. Make sure there is no investment, dirt, or contaminants. Be sure the models are also clean.
That happened to me once a long time ago. It ended up not just being a bad box of investment it was a bad pallet-full. I was casting wax carvings for a jewelry store and using Kerr Satin Cast. It took forever to figure out what the problem was.
Eventually the tool company that I bought the investment from set me up with a phone call to a Kerr tech support specialist. I had always mixed investment by eye, because I cast so many flasks for so many years.
The Kerr specialist talked me into measuring everything precisely and following their mixing instructions and burn out schedule exactly. Ever since then, it has become a habit and that’s what I do.
So two things. Yes it’s possible to get a bad batch of investment. And I’d call tech support from whatever investment that you use. They might be really helpful in you sorting out your problem.
I’m sorry you’re going through this! It’s a huge pain to deal with!
Thanks for your advice! Yes I do follow the recommended investment and burnout procedure by R&R and precisely so, always have.
I can’t imagine the frustration you must have had casting for a store. I’ve been getting maybe 50% patterns being scrapped and I imagine after a couple months I’d be out of excuses for my employer . My solution so far has been just to cast 2-3 copies of everything and praying that one comes out without a blob. I’ve had to outsource all my gold casts as mistakes like this would be far too costly for me to bear.
Out of curiosity - I have to ask if anyone knows why the investment must boil in the flask? Considering the entire point is to remove gas from the investment, and boiling is turning the water into gas, isn’t that counter productive? Would it not be better to invest ice cold water to prevent it from boiling at all? Just a thought.
Following this discussion as I have, I am glad that I made the decision years ago not to pursue lost wax casting. I still have the kiln and an unused HR centrifugal casting arm purchased from Gesswein as a kit probably 40 - 45 years ago. I have since rebuilt the kiln and added a controller, but the arm still sits in a box on a shelf with nothing to do. Casting never really appealed to me. It seems more like a science or craft and less like an art. To me the art is in making the wax model. After that, look for someone well versed in the science of casting to make your castings. I also don’t make a lot of the same thing, so it makes sense that casting is less attractive to me than it might be to others. Just my $.02…Rob
As far as I know the second vacuum in the flask is to insure that the investment gets into every crevice of the model and to insure that no air bubbles attach to the model.
That’s a slightly different reason than just eliminating gas in the investment.
One other issue for you to consider, is that you’re 3/D printing right? Maybe something has changed with the 3/D printing media you’re using? I’m no expert at 3/D printing so I’m no help there.
No matter what I hope that you solve the mystery soon! Fingers crossed!!
The reason you want to boil the investment at room temperature is to bring any small bubbles to the top, where they will break. It’s usual to boil the freshly mixed investment in its mixing vessel first, then to pour it into the flask around the waxes or resin parts and boil it again. The boiling action dislodges any small air bubbles that may be clinging to your patterns. But it’s important that you have enough vacuum pressure to actually get a rolling boil. If you’re just short of that, it will be worse than useless, since it will actually create gas bubbles around your models, just like the ones you see lining a pot of water on your stove before it comes to a boil.
Well for all who are following this thread - I tried Optima Prestige and followed all their standard procedures. I got a flawless casting, just as I’ve been used to. I’m convinced the last 4 boxes of R&R investment I’ve received have been bad. I just didn’t expect that to be the problem. I can’t imagine why the investment itself would cause severe bubble defects.
. My solution so far has been just to cast 2-3 copies of everything and praying that one comes out without a blob. I’ve had to outsource all my gold casts as mistakes like this would be far too costly for me to bear.