Greensand Tests

[vtsteam]

I'm going to break this topic out of my oil fired furnace thread, since that one is really supposed to be about my furnace.

A few days ago I decided to gradually test my way up through some green sand recipes by starting out with US Silica F60 silica sand, and Whittaker bentonite 149 (probably sodium bentonite, but not definite).

The procedure would be to start at about 4% clay and 4% water, and do a trial, then increase the clay percentage and repeat, until I felt the greensand produced good results with the minimum amount of clay, specifically for my sand and equipment..

For the first trial, the ingerdients were mixed in the proportion of 50 lbs sand  to 2 lbs, clay, or a little less than 4% bentonite, dry weight. 2 lbs of water was also mixed in.

I waited a day for the clay to full absorb the moisture, and have checked it for a few days since.

Conclusions:

It is way under-bonded.
It is also way too wet.

In fact, I rate it as unusable as-is, just by feel.

Therefore I've added 1/2 lb of additional bentonite, to bring the clay percentage to a little under 5%. It was thoroughly mixed in and returned to a plastic tub for aging. 

No additional water was added. Water reduces through slow evaporation over time in this setup. When the sand reaches a state were the clay bonding feels sufficient, I will correct the moisture to 3%, as measured by drying and weighing a sample.

[Fredbare]

Thanks Vtsteam, as a newbie to casting, I'm also having problems trying to get the correct mix, of bentonite, sand, and water,  and that is useful info, thanks for sharing.

John

[vtsteam]

Glad it might be of help John.

Just to show why there is confusion over it I'm compiling a list below of the few greensand recipes for iron sand for small (under 50 lb) castings I have found, and giving the source. As you can see, there is almost no agreement at all between these.

Stewart Marshall, "Building Small Cupola Furnaces,"
100 lb fine silica sand
10 lb Southern Bentonite
15 lb fireclay
3 lb fine seacoal
7 to 10 lb water

(This mix appears to be a whopping 19.5 % clay (mixed fireclay and bentonite) and 5 to 8% water)

Steve Chastain, "Metal Casting: A Sand Casting Manual For the Small Foundry"


95 lbs #120 Olivine Sand
5 lbs Western Bentonite
3.5 lbs water

(This mix has 5% clay and 3.5% water. Western bentonite is sodium bentonite)

W.C Ammen, "The Complete Handbook of Sand Casting"

(No actual iron sand recipe, but lists iron sand fineness as a mix of #80 and #110)

US Navy "Foundry Manual"

89.4 lbs #70-100 Silica sand
5.3 lbs Bentonite
5.3 lbs Fireclay
2.5 lbs water

(Total clay content is a respectable 10.6%, water is a dry 2.5 %)

Colin Pack, "The Artful Bodger's Iron Casting Waste Oil Furnace" (poundage interpolated)

101 lbs Sand (natural)
9 lbs Bentonite
about 1/2 satchet wallpaper paste

(Total clay content is 8%, water not specified)

And last but not least,

Ironman, from his YouTube video (poundage interpolated):

88.5 lbs fine sand
7.5 lbs Bentonite
4 lbs Seacoal (later dropped from recipe)
4 lbs water

(Total clay content is 7.5%, seacoal is 4%, and water is 4%)

[ironman]

Don't you just love all the confusion and I am adding even more confusion.

When I started casting I tried to read as much as I could and was very irritating because they all were different.

What I to had to understand was that everyone has different levels of experience and understanding of the subject and also materials differ from I have to what is being used in the book webpage etc.

The bentonite I use is mined in Australia and could be different to what you are using.

[vtsteam]

It is funny Ironman. I'm sure ingredients differ everywhere, so I think people just have to experiment and work their way through it.

You haven't added anything to the confusion as far as I'm concerned, but exemplified how a person can work through to a very focused and efficient way of casting with what is available locally.

I hope I can do that as well. I'm sure that given enough time, and If I don't give up, it will eventually fall into place with what I can get locally.

I think the only time a lot of this is easily transferred is if someone else local with the same materials visits a successful caster and then adopts that experience. But it's pretty tough to try to cross continents!