School me on sand (greensand and LF)

While I prepare for the furnace build I figured I should start learning the rest I need to get started. I plan on starting with lost foam as I do mostly one-offs (already started designing a hot wire cutter). But it would be silly not to learn about green sand as well while I'm at it.

So, how complicated have you guys managed to make this?
I see most specify quartz and or silica sand, which technically isn't necessarily the same. I've also seen olivine (IIRC a magnesium-iron silicate) sand mentioned. But are we talking "high silica/quartz content" or pure (95% +)? Or put another way, what would be a waste of time to even try? Remember I'm in Norway so I can't just order a bag of foundry sand.

 

Here are the keys to the kingdom:
https://www.hnsa.org/manuals-documents/single-topic/foundry-manual/

No, it's absolutely not a waste of time to try. My greensand is white sandblasting silica sand. It's fine but I don't know how fine. My neighbor had about 75 lbs of it, so that's what I used. Mixed with bentonite clay, I think 8% or 9% by weight. I think my water runs about 6% or so by weight. It's been awhile because I switched to petrobond (oil bonded sand) a few years ago. It worked ok as far as refractoriness but my surface finish was never great. I had a choice to either refine my sand mixture or invest in petrobond. I was lured toward petrobond as a cure to the inconveniences of greensand which it is to some extent, but it's no panacea. So, yeah, go for it.

Pete

 

Cool, those old manuals can be real gems.

Edit: WOW, that book looks awesome. A real "Get Shit Done With What You Have" book. Exactly what I need.

 

One problem is finding fine enough sand. I have a few options (sandblasting/filter sand) in the 25-70 mesh range, but that's about it. Most sources seem to recommend 70-140 mesh, and although I suspect coarser would work fine for coated LF it would be nice to standardize on a single sand for both green and LF. What about natural sands?

 

This is the setup I used to refine sand from the big box stores for green sand.



Put the sand in a bucket, slowly pour a cup at a time on the board and let it bounce into the air stream.
The heavy grains will be closest to the fan.
Fold the tarp over to consolidate the sand into a line.
Divide the line into thirds.
Bottom third becomes lost foam sand, middle third is backing green sand, top third can be facing sand.
Or, just divide in half and use top half as green sand.
You can do a bag in about five minutes.

 

Clever. I have collected a couple kg of playground sand so I can get a feel for the different grades before I make a decision. I washed it with water to remove the bulk of clay/organics, after drying I'll try your trick for sure. I do have a couple of small sieves (only 4-5") so they're only good for grading samples. But it should at least give a resemblance of empiricism to things.

 

Wow, OK. I had no idea the sand you guys use would be so fine. What I usually call sand is way coarser, I probably washed out all the usable fractions when cleaning it (virtually nothing passes 120#). I really should have known better, because I always found it weird that you could get such fine castings from what I thought of as "sand".

 

Petrobond is usually 140, it'll pick up a fingerprint.
Only about 25% of the bagged sand is decent casting sand.
That's why you need a quick process that will separate the fines from the rest.
I've been there with a mesh screen, it takes all day to get a few kilo's.
Wear your dust mask if you try it.

 

I don't really have any suitable fans, perhaps it's possible to use water to do this?

 

Ugh, wet sand. There is little worse than having wet sand and wishing it was dry.
Once in awhile we have to get a little creative and start thinking outside the box. If every topic simply ends with "don't have one can't get one" none of us would get anywhere. Options? In this case: take the box fan out of the window while she's at work, thrift store, yard sale, vacuum cleaner or other appliance on the side of the road that might have a fan in it, etc. Follow me?
You don't have to be a master fabricator or have a garage full of fancy tools or a big bank account. Those things all certainly help but the things we need are often things we've never needed before but are hiding in plain site.

Pete

 

I don't know how you would do that.
Besides, the sun is getting pretty low in the sky to be drying 50 kilo's of sand.

 

I know, wet sand is a drag. But then again any natural sand I can get will be wet or at least moist. The best I have found commercially is 25-140#, that should work but there will be a lot of waste.
According to the all-knowing internet the settling velocity of 100# sand should be in the 1cm/s-range, so it shouldn't be too hard to do. I'm doing a little small scale test as we speak, and it looks somewhat promising (but messy).

Come to think about it I do have a reversible "wet&dry" shop vac, I might be able to rig up something with that. Guess I have a few options to play around with.

 

Guess one is never to old to play with sand... Mixed up a pound of green sand using 8% of bentonite and appr 10% water. Seems to work fine, I can squeeze it into a ball that breaks cleanly. Here's a quick test of it's molding capabilities:

Edit: Better pictures.
What do you think? It's a bottle cap, and the ridges are perhaps 1/10" deep.

 

By gosh that's it! Use some parting dust to cover your pattern prior to ramming. It's to prevent sticking of the pattern as well as mating sand surfaces. Some use chalkdust available as chalk line refill from the hardware store. Put it in a sock to dispense it.
Your sand may behave a little differently after its sat overnight and the water has really absorbed into the clay.
Very nice.

Pete

 

Yeah, it gave me a real "this makes sense" experience. Now I know what I'm looking for. I could also feel it improve with each try, the worked sand got more pliable. I'm sure a muller would be sweet, but that's too much equipment for me right now.

I'll try to do some more work on water grading sand this week. I have plenty of natural sand at work I can use, and since it's wet anyways it wouldn't do any harm. The basic idea is to put a bucket in larger tub and run water in at the bottom of the bucket (nozzle aimed at the bottom to promote laminar flow). The tub would catch the fine sand while allowing the clay and most of the silt to wash off.

 

It's much easier to suspend clay and silt in water than sand so it seems to me like that sand washing method should be viable. Let us know how it works for you.

 

Here's my setup:

The sand is then washed using a garden hose aimed straight down while stirring for appr 30 seconds.
This is the result:

Of course you don't have to empty the tub for each bucket. There are some coarse rubber granulate in the sand, but that can be sifted out with a coarse strainer.

I also made a couple of videos (appr 15-20meg each) of how the sand behaves, it should give some indication on grain size:

https://we.tl/t-h9nkr0qavW
https://we.tl/t-doxPFnOA5k