Reuasbale Offset Pouring Basin

When I bought it was $40/gal, now it's double that, at least from that source, and yah the tube price is pretty silly. In fact I think I paid $180 for 5gal when I built my low mass furnace with it. For one of those tubes and 12x24x.5 board you could probably build 4 or 5 cups.

You can try but me thinks same result.

Best,
Kelly

 

It's the same problem hobbyist always have with buying professional materials......convenience factor (especially online) and large unit cost for small quantity buy when the product is more typically sold in >5 gallon buckets to foundries. I still have 3" left in the 5 gallon bucket I bought for my furnace build, so my unit cost is low. I get/got mine from my local refractory products supplier but that wont work for anyone else. They carry the Harbison Walker product which is branded Inswool, but there are many brands. It's all ceramic fiber suspended in Alumina-Silcate goo. I'd recommend anyone else look for local supplier and save that, search moldable ceramic fiber. Personally I wouldn't be without it.

I've seen it referred to as pumpable, glue, moldable, paste, putty, and mastic. The only difference is viscosity. The thinner stuff is good for glue and the thicker for hand molding/placement.

Here's a tube for $20.

Inswool Pumpable Caulk (clay-planet.com)

Best,
Kelly

 

Thinking about this, if you wanted to try an offset lost foam pouring cup with no out of pocket cost, I mentioned sodium silicate, but you might be able to make a simple core box and mold one or a couple out of green sand or petrobond. It would not be reusable but you might even be able to recover the bound sand and reuse it.

For me they were essentially free since I had the stuff left over after making the purchase for the furnace build, but it's great to have for maintenance and high temp sealing. When purchased in qty, the unit cost for a cup is quite low, maybe $5 depending upon size but of course that assumes you have use for the rest of the material. When you consider with care and occassional maintenace, you can get several hundred of pours out of a cup the recurring cost per pour is quite low.

I remarked on it's properties earlier in the thread. Completely non-wetting, high service temp, impervious to thermal shock, highly insulating, relatively easy to work with and store, but it does require occassional mainetnace, and need to be fired before use, albiet a uncontrolled temp shedule. I haven't found another material quite like it.

I bought my material 4 years ago. Some of these products say they have a shelf life. Mine hase been stored in the sealed 5-gal bucket of purcahse and performs the same as the day I bought it. It's a shame that like everything else prices have doubled since. Even the ceramic fiber board. At that same time you could buy a 12 x 12 x .5" board delivered for $15......sighh.

I wouldn't bang on about it so much, but I was surprised by their performance and how they positively contributed to my results. When you want professional results, sometimes there aren't good hobby substitutes for pro materials.....but they wont fix poor casting design, molten metal mangement, or technique.

If anyone does decide to make reusable moldabe ceramic fiber (MCF) version, there are a few must haves and must dos.

1. They must have draft - I chose 5 degrees
2. They must have a wier and better if one of the more proven shapes
3. The inside corners must be filleted to prevent metal penetrating the crevaces....it prevents damaging the cup when the residual foil skin is removed afterward.
4. They must have a metal lifting cradle you can grab with pliers to remove and dump them after the pour.
5. If you use a combo of board and MCF, you must coat the friable cut board surfaces with MCF.
6. 2300F ceramic fiber board works fine but 2600F rated is better, not that you need the temp, but because it's denser and more durable, albiaet harder tofind and more expensive.
7. ....and of course, you must remember to pull and dump the cup immediately after the pour while the metal is still molten.

Best,
Kelly

 

Especially if you use a little more SS than you normally would for a core........and perhaps fine sand.

Best,
Kelly

 

Looks the part. Did you fire it?

Best,
Kelly

 

Not familiar with it. What is the density? If you have sodium silicate (water glass), you can use that as a binder for plain sand and cure with CO2.

Lindseed oil was a common core binder mixed with sand, then baked. I've never used it but if good enough for cores should be ok for cup?

If the foam is just a plug to form the shape, that's fine but remove it (burn out) and whatever material used, fire it to well above the pouring temp to make sure it doesn't offgas during th epour. Even so it can be hard to keep some materials from breaking due to thermal shock.

As I mentioned in your other post, low mass and low conductivity so it doesn't steal heat from the melt. The test pour you mentioned would be worth it just to test your cup.

Best,
Kelly

 

It can/will depend on the grade of SS and mesh size of your sand, but the criticality of this is to achieve core strength that is strong enough to hold its shape under heat, yet still shake out and not be a rock hard core that can't be removed from the casting. For your purposes, rock hard is better so dont be afraid to be on the high side of SS content.

For RU grade SS, 4-5% by weight but if you have more dilute SS, it could be double that. Make a small sample. Cure it with CO2 and use a lance you can penetrate the sand with. Some modest low temp (100-150C) baking may be helpful to get full cure, but if you use a foam plug you will need to burn that out at higher temp. The foam will only reliably stand about 130-140F. After the sand is hard it doesnt matter.

Here's a thread but if you search the forum you will find more. You can ignore the stuff about adding sugar or sea coal. The former is to weaken the core and latter to make it more compatible with iron.

Sodium Silicate RU for core making in cast iron molding. | The Home Foundry

Best,
Kelly

 

I took a spin back through this thread from the beginning. It's worth doing for anyone that is a serious lost foam caster and considering making a pouring cup. The thread starts four years ago and I was still using mud as my coating (not that there's anything wrong with that) instead of the commercial refractory coating I've been using since. The most important aspects of the cup are the shape and the material and I am still amazed at their contribution to (my) process improvement.

Shape: I recommend the square shaped ones with square sprues. It must have a wier. The square basin and square sprue will be less prone to aspirating air, and along with the weir they do their job extremely well. Square sprues are very easy to make and work better than round ones. They can be easily tapered too.

Material: It's key to cups being reusable. You just can't beat the moldable ceramic fiber/pumpable ceramic fiber (MCF) or combos of that with ceramic fiber board (CFB). It's totally non-wetted by aluminum, highly insulating so it robs no heat from your melt, is impervious to thermal shock, and indefinitely repairable. It is spendy, but I built four cups four years ago and am still using them with somewhere between 100-200 pours across the lot......not much cost per pour and the cost/pour is only going down with time.

Not sure I can say it better than this 12 minute video back in post 42 re-posted here for convenience.



But, depending on how often you cast and the nature of what you cast, reuse may not be as important to you, material availability and its cost may not be as justifiable, and alternative (on-hand) materials seem to be the direction this thread is heading.

Having already invetsed the time to make mine, I'll just opine from the gallery in case it's of use.

In that regard, I'd suggest keeping any alternative material's density low, and insulating properties as high as possible so it doesn't rob heat from the melt, and of course be relatively easy to make. I dont think there is a less expensive material that does that than sand and binder, and probably sodium silicate. I say this because sand is cheap, and fairly insulating.....now more or less so than the rest of the mold. Sodium silicate is inexpensive and can be almost instantly cured and making a cup is no more effort than making a core for a mold. If you made a decent cup mold with a good cup design, you could probably make them a handful at a time in a few minutes. It's also possible with elevated amounts of SS, they could be durable enough to be resued some number of times, but you would still need a lifting cradle and you'd probably need to accept they would have an aluminum skin that builds up over time and degrades performance.

Making a SS core certainly seems to be within the practical reach of most hobby casters.

If you made a good cup mold with thick enough walls, it's possible a one-use cup could be green sand.

It's really a matter of what it's worth to you. If you have a few minutes into pattern construction, you're not out much if it fails. However, if you have a few hours or days into the pattern......

Best,
Kelly