Oil Sands for casting - any "home made recipes" ?

[DGentile]

I'm still getting into the whole casting stuff a bit - but figured, that so far the plaster-type stuff I use is quite troublesome - don't know if I get the mixing all wrong or what, but it ends up way too porous or brittle... anyways I've used up the last I've had anyways and have no intention on getting the same product again.

 

well I'm trying to get casting to work for me for fittings of all types but sometimes also for reproduction of machinery pieces (small stuff)...

Detail is important, but not that much, I mean I'll have to rework surfaces anyways a bit - so I was thinking of using oil-sand for castings... it looks a hell lot easier to "get things right".

 

now the question is -> "Oil Sand"? What exactly is in it, I mean, can this stuff be "made in the shop" out of "common" ingridients?

or is that some sort of special chemistry?

at the moment my cash for experimenting with things is "simply very very limited", so if I can make the stuff cheaply instead of buying 25kg (minimum with most suppliers here as it seem) it would be really good.

 

any other input or ideas?

 

daniel

[Jeroen Zuiderwijk]

If you want to make it yourself, definately check Backyard Metalcasting for tips. Mind though that if you just use sand, the grain is very coarse and is not good for fine detail. That's why I prefer to buy the stuff instead. The stuff I use is Bindol sand. It's not actually sand, but a very fine clay powder (might be bentonite, but I'm not sure). Just to show what can be achieved with Bindol:

http://1501bc.com/metalworking/08100002.jpg

These fibulae are about 8cm, and every detail is exactly as the model (even copies scratches etc. from the models). You can sometimes even copy fingerprints with the stuff. If the relative volume of the cast gets larger, the detail gets lower though. You might need to go to a coarser sand for bigger castings.

[B. Norris]

I'm still getting into the whole casting stuff a bit - but figured, that so far the plaster-type stuff I use is quite troublesome - don't know if I get the mixing all wrong or what, but it ends up way too porous or brittle... anyways I've used up the last I've had anyways and have no intention on getting the same product again.

 

Daniel,

 

Most of the commercial, casting investment is intended to have oxygen removed under a vacumn bell. I just watched a clip on lost wax casting, on YouTube, the other day and the guy pulled a vacumn after mixing and then again after the investment had been poured into the flask. As an aside, the plaster like stuff you had is extremely fine and VERY bad for your lungs. A respirator should be used when mixing the stuff.

 

~Bruce~

[Guy Thomas]

In particular check out this from the Backyard Metalcasting site Jeroen gave you the link for:

 

http://www.backyardmetalcasting.com/greensand.html

 

If you try the route of sifting common builders sand first make sure it is a pure silica product as you don't want bits of limestone and such in it. Also when sifting wear a respirator! You would not believe how much fine silica dust this activity creates. It's also a royal pain in the arse and time consuming. If possible try and find a very fine pure silica sand blasting product which won't require sifting. Another route though is to find a foundry near you and see if they will just let you have some of their sand either for free or for a small price.

 

I'll be curious how you progress as I haven't gotten past the "finding a suitable silca sand" stage myself. Might be another reason for me to go to Batson's Bladesmithing symposium this year as Birmingham, Alabama is an old steel making center and things like fine olivine sand can be purchased there. Not being a manufacturing center of any kind Tallahasse where I live is devoid of raw materials like that.

[DGentile]

Daniel,

 

Most of the commercial, casting investment is intended to have oxygen removed under a vacumn bell. I just watched a clip on lost wax casting, on YouTube, the other day and the guy pulled a vacumn after mixing and then again after the investment had been poured into the flask. As an aside, the plaster like stuff you had is extremely fine and VERY bad for your lungs. A respirator should be used when mixing the stuff.

 

~Bruce~

 

Yes, I luckily I was VERY AWARE of the dangers involved and always wore my trusty respirator... When I called the company who sold it to me and wanted to order the first time I asked whether they have small quantities (instead of 25kg) - and the guy said: "Nah, we don't do that - we don't want to open the packages and have the dust anywehere or breathe it in - it's bad - and wearing a respirator isn't something we want to deal with in our storage rooms anyways - so no small quantities".... I guess I got the message

 

However I didn't know about the vacuum... that makes sense - and explains a few problems I had.

 

thanks

[DGentile]

If you want to make it yourself, definately check Backyard Metalcasting for tips. Mind though that if you just use sand, the grain is very coarse and is not good for fine detail. That's why I prefer to buy the stuff instead. The stuff I use is Bindol sand. It's not actually sand, but a very fine clay powder (might be bentonite, but I'm not sure). Just to show what can be achieved with Bindol:

http://1501bc.com/metalworking/08100002.jpg

These fibulae are about 8cm, and every detail is exactly as the model (even copies scratches etc. from the models). You can sometimes even copy fingerprints with the stuff. If the relative volume of the cast gets larger, the detail gets lower though. You might need to go to a coarser sand for bigger castings.

 

Jeroen, thank you for the link and picture - nice work btw!!

I actually knew the link, but didn't remember that he had instructions for the sand there ... I found it ... very easy.

 

daniel

[DGentile]

In particular check out this from the Backyard Metalcasting site Jeroen gave you the link for:

 

http://www.backyardmetalcasting.com/greensand.html

 

If you try the route of sifting common builders sand first make sure it is a pure silica product as you don't want bits of limestone and such in it. Also when sifting wear a respirator! You would not believe how much fine silica dust this activity creates. It's also a royal pain in the arse and time consuming. If possible try and find a very fine pure silica sand blasting product which won't require sifting. Another route though is to find a foundry near you and see if they will just let you have some of their sand either for free or for a small price.

 

I'll be curious how you progress as I haven't gotten past the "finding a suitable silca sand" stage myself. Might be another reason for me to go to Batson's Bladesmithing symposium this year as Birmingham, Alabama is an old steel making center and things like fine olivine sand can be purchased there. Not being a manufacturing center of any kind Tallahasse where I live is devoid of raw materials like that.

 

We only have a very limited number of foundries.... and none here in my neighbourhood... so that's not much of an option, at least not for now...

And I once asked a larger foundry whether I could buy small quantities of them, and the price was so ridiculous that I could have gotten a whole bag from a regular supplier instead - deliverd to my doorstep.

 

thanks for the tip on the respirator when sifting the sand.... actually I might be able to get fine silica sand easily here ...

 

 

one question ... after reading the text on backyardmetalcasting.com he says:

I moistened the sand slightly then sprinkled a percentage (the percentage depends on formula you use and type of clay you have) of clay onto the sand and began mixing it in.

 

now - how do I SPRINKLE CLAY onto something???? I mean clay's not exactly liquid .... or do I dissolve clay in water until it becomes a slurry and then sprinkle that on top... but then that would make "moistening the sand" a bit obsolete, wouldn't it?

 

??

thanks again

[B. Norris]

Daniel,

 

I think the clay he is using is dried, powdered, clay from a pottery supply place. If you cannot get it, buy the wet stuff, let it dry, and then pulverize it! Sounds too much like work to me, I'd go for buying it predone. If you have friends who are potters you could offer to sweep their shop for a week, you'd have all you need! I imagine having the sand damp helps the clay stick to the particles and bind them together better.

 

~Bruce~

[Alex Brydges]

When i took casting and mold making in college, we started out using ceiling tiles as the mold. You carved out your piece in one tile (or both by flipping it over and tapping the two together on the table to get a sort of dust registration mark on the second tile). you then carved your sprew and funnel, sandwiched the two together with c-clamp (metal plates on the outside), and cast away. Pretty crude, but very effective. Oh, and the tiles dont burn up because they are made of some sort of fire retardant.

As to getting a fine grade casting, we used the lost wax method with a sort of plaster mold. You have to use an aggregate with the plaster, and obviously that will effect the surface texture of your casting. i found that using the discarded sand from a sand blaster (sent through a fine mesh to catch any surprises) was the best and cheapest solution. Make sure you know what was blasted in the sand blaster (ie aluminum+rust+molten bronze= strange texture on the casting where it turned to thermite)

To get the air out of the solution, i added a very very small amount of dish soap in the initial mixture(a drop the size of the head of a finishing nail should be enough) as a surfactant to break the surface tension on the poured mixture. Then just shake/tap, but very gently(dont want to break those sprews/vents).

Hope this helps.

-A

[Jan Ysselstein]

any other input or ideas?

 

daniel

 

Daniel,

 

Oil sand is messy and can be problematic with bronze. I had to look a long time for someone to take it off my hands as I did not want it in the land-fill. I have visited a foundry in Idaho which does mostly silicon bronze door hardware every day, fascinating!

 

When I got home I experimented with their process and it is fool proof (once you get the shrinkage of molten metal concepts ). They use about 4-5% bentonite clay and olivine sand (you adjust it if you find it too sticky or not sticky enough). I do not remember the mesh size, but I believe I bought a bag of 80 mesh and a bag of 120 mesh. This system worked very well, I made the flasks out of 2" angle iron and the mold release was a little graphite powder in 99% isopropyl alcohol (rubbing alcohol), the parting compound was talcum (talc). We have a spray graphite lubricant (auto supply stores) by Mc Kay which should work well as a mold release also. A silcon mold release spray may also be used to pull the pattern from the rammed sand.

 

Be sure to add weights on your top flask to avoid mold lift and leakage out of the seam of the two molds.

 

Sands and binders require very, very thorough mixing and intimate contact of the binders with the sand. This is not easy for the amateur, I have found the best system is to mix it as well as you can with a rake, gather it and stomp on it to compact it.....then cut it (scrape it) with a blade like a sharp garden hoe or grub hoe, stomp again and repeat this cycle at least 3 times. The cutting action slices through the areas which are not mixed properly and redistributes them.

This mix can be stored wet for later use.

 

For those patterns which must be done by lost wax casting, my recommendation is to make the pattern, look up a local art foudry and have them cast it for you.

Good luck and Be Careful!

 

Jan

Edited February 8, 2008 by Jan Ysselstein

[Matt Bower]

Daniel,

 

With regard to backyardmetalcasting.com, don't just read the main pages. Go to the forums, read and ask questions. You'll learn a great deal there.

 

Pottery suppliers are the backyard hobby caster's best friends; I'm fortunate to have a couple good pottery supply shops within 20 minutes or so of my house, and I've bought lots of stuff from them (most of it for things other than casting). They carry all kinds of stuff you won't find too many find other places: clays, useful chemicals , ceramic fiber, firebrick (both hard and insulating), alumina, very fine silica sand, etc. Yes, the clay mentioned on BYMC was dry, powdered clay. For greensand, which is casting sand bonded with clay and a little moisture, bentonite is a commonly used clay. (You'll fine recipes on the Internet if you look around. Southern bentonite, western bentonte, various proportions of both . . . ) Proper oil sand normally uses organo-bentone, which is bentonite clay that has been chemically altered so that behaves in oil the same way that regular clay behaves in water; i.e., absorbs the oil and becomes sticky, which is what binds the sand together. Mixing oil with regular bentonite clay won't give you real oil sand; it'll just give you an oily mess.

 

I haven't quite figured out where to buy organo-bentone, yet, so I haven't tried making my own oil sand.

 

Jewler's supply shops sell high quality investment, carving waxes, etc., if you want to get into investment casting. A lot of folks do investment casting using Plaster of Paris grogged with silica sand, but it's somewhat iffy and I'd be very hesitant to try it with higher-melting metals (brass, bronze, silver, etc.)

 

Ceramic shell investment casting is a great method for fine detail and great surface finish, but it's fairly expensive and time-consuming, and you have to know what you're doing.

 

Jewler's supply shops can also sell you very fine, oil sand-like material that I believe is actually made from clay. You use it like regular oil or green sand, but it provides a very fine surface finish. Delft Clay is one kind. It's not cheap, but it is reusable.

 

By the way, I'm not a very skilled caster; I've just read a lot about it. (I've done some rather crude castings, but I haven't had the time to really get into it. Someday . . .)

[JJH]

Green Sand

50 kg sea shore sand (I'm guessing silica)

1 litre of water

8% Bentonite Clay (avalible at potters supplies or some kitty litter if your willing to grind it)

 

Oil Sand

100 parts Silica Sand

2 parts Water

2 parts Dextrine or Cereal binder (I've been told black treacle or starch works)

1 part Linseed Oil

 

"Oil Sand prepared soley from silica sand, although having enough strength after baking, may well be found difficult to handle as cores in it's green state. That is why a happy medium needs to be found and a proportion of red moulding sand say 50-50, is substituted. The result will be some sacrifice of dry strength, but an improvement in handling quality green. A small addition of fullers earth may also show an improvement"

[Matt Bower]

Ah, that's a different kind of oil sand. It's using oxidized linseed oil as the binder. Can it be reused?

[JJH]

Your guess is as good as mine thinkng of building a foundry for wootz and cast iron and have collected a few books this is a recipe from foundrywork for the amateur

[Matt Bower]

I would guess that the sand isn't easily reusable. Once linseed oil hardens it doesn't really un-harden, to my knowledge. The advantage of Petrobond and similar oil sands, and greensands, is that they can be reused repeatedly with occasional topping off with fresh oil or water/clay. The recipe you have there looks very much like one for cores.

 

What sort of furnace are you thinking of for the cast iron? I'd love to build a cupola, but I really don't need the capacity to produce large quantities of cast iron.

[A Flor]

I would guess that the sand isn't easily reusable. Once linseed oil hardens it doesn't really un-harden, to my knowledge. The advantage of Petrobond and similar oil sands, and greensands, is that they can be reused repeatedly with occasional topping off with fresh oil or water/clay. The recipe you have there looks very much like one for cores.

 

What sort of furnace are you thinking of for the cast iron? I'd love to build a cupola, but I really don't need the capacity to produce large quantities of cast iron.

 

Petrobond is commercially made.

Gives great definition.

It's spendy, but by the time you shift through sand, mull, oil plus your time, may be worth it to you.

Visit My Website

 

I use a Gingery Furnance.

The center lifts up so the cruciable comes out horizonally.

(Don't have to look into the furnace and lift "up' hot metal.)

I've not tryed it with iron.

But it will melt brass and bronze with no problem.

Can be made with scraps of angle iron, pipe, sheet metal and common hardware.

I used a refractory for the walls. (As I recall, about $80.00)

Good luck.

Visit My Website

[JJH]

I'm collecting the stuff to build "The Artful Bodgers Waste Oil Foundry" The guy has melted 60lbs of iron in it though it took 2 1/2 hours. A friend want to do iron and I'd like to do wootz.

[Ken Kelley]

Dan,

 

I use the recipe mentioned in this web site http://www.foundry.ray-vin.com/k-bond/k-bond.htm I've had excellent results with it and the materials are easily obtainable.

[Jerrod Miller]

I don't meant to bring up such a long-dead topic, but this was the first hit on a site search for sand casting and I wanted to add some info.

Every now and then I get to go out and do casting demos for work (schools, career fairs, etc.). I have also done heat treat demos with W1 drill rod (bobby-pins work too) showing annealed/normalized vs. as-quenched vs. quenched and tempered. But this is about casting.

We got the Foundry-in-a-Box. http://www.afsinc.org/career/content.cfm?ItemNumber=13109

It uses the K-Bond sand that Ken linked to (as of today that link still works too!). I have been using the kit for over 100 castings in the last year, with the sand exposed to wide temperature ranges in storage. We keep the sand in a Rubbermaid knock-off bin, it is loose enough to leak sand. I just use tin, as the microwave didn't really do anything to the aluminum shot I tried in it. I asked Tom Cobett (Ken's link says that it was one of his students that developed the mix) if it was good for other things too (higher temp). He said he regularly uses it for aluminum, brass/bronze, and thin section grey-iron. Steel temps may lead to lustrous carbon in the mold that may be problematic, but it may be fine too. In case the link Ken provided ever goes bad I am adding the info that Tom sent me today (I asked and he said I could share it). This stuff is pretty good.

[Scott A. Roush]

This is interesting. I keep hearing of using microwaves for stuff like this. What kind of microwave are they talking about??

[Jerrod Miller]

"Standard" kitchen style. It has the markings on it telling you recommended cooking times (popcorn=3 min, etc.). The bottom (at least) should be ceramic (ours is) because you do it enough and you are bound to knock the crucible off of its refractory brick and spill liquid tin (or whatever). I did that last week after a few hours of running and had zero problems cleaning it up. Had to remelt the metal so it added about 2 minutes to the demo to clean and remelt. It is all packed away right now so this is the best picture I have on hand to share with you.

Kit:

 

Sand (K-Bond):

[Miles Hebbard]

I used to have a 3 mag catering microwave that you could use steel dishes / pots in, it could turn a piece of steak into a brick in 5 min. Damn scary thing to coock with...

[Miles Hebbard]

I used to have a 3 mag catering microwave that you could use steel dishes / pots in, it could turn a piece of steak into a brick in 5 min. Damn scary thing to coock with... Years ago I did some casting with silicone, liqud, with an activator, mostly lead, held up well +- 20 castings, detail is magic, release good but darn expensive! And a vacum chamber is a must!