What is the "right" amount of moisture for greensand?

Sand casters might want to consider investing into a dehumidifier and keep your sand in a water tight environment/box/container.
Dehumidifiers can be cheaply purchased on line.

Of course, the dehumidifier would only be beneficial with Petrobond or other oil based casting sand.

 

You beat me to it. Lol
Chirpy sounds like he’s on his game and doing it the correct way.

Without one your just guessing.

 

You know Jeff, I heard that if you shovel a spoon full into your mouth and it sticks to the roof of your mouth then it’s too wet.

 

Ok, I’ll get cereal here.

Per LSF Foundry Solutions the moisture content/level is suppose to be 3%, max.

http://www.solutionsfonderie.com/20...ies-should-you-control-per-molding-equipment/

 

I have no notion of the correct percentage number, yet. But, another way to check moisture content that requires only a decent kitchen, postage, or even better, lab scale would be to simply weigh out a convenient amount of sand and then stick it in the oven at 300 deg F for an hour or two. Compare the wet weight to the dry weight and calculate the percentage difference. I have used this method to check wood moisture content---by no means a new idea. I prefer this method over a meter as you have no way to know how accurate or repeatable a "meter" might be. And you could verify a meter this way too.

The local aluminum foundry owner has calibrated his hand through 40 yrs of experience casting!

Denis

 

I believe the 3% quote is for initial wet out and then brought down to somewhere around 1.4% or just enough to retain a good strength within the bentonite so it binds the other aggregates.

 

unless you are going to buy one of these... http://sandtesting.com/product/rapid-moisture-tester/
which was exactly what we had in the Navy I recommend the fistful test, take a fistful and squeeze it , it should form an interior shape of your hand ball and stay together, then throw it against the wall, most of it should stick , it should not feel wet, only moist, if you squeeze water out it's mud, and if it has too much clay, it will take too much water to make it stick, add sand, and let it dry, also if it is not sufficiently mulled to coat the sand with the clay it will take too much water to make it stick, and also too much moisture, the way to do it is to weigh out ALL THE INGREDIENTS IN ADVANCE. mull the sand and binders sufficiently about 11 minutes, and add the appropriate amount of water , you can get the recipes from the Navy Foundry manual, cereals and clay will need a small addition after each pour, the amounts of make up binders depend on the surface area of the casting compared to the total amount of sand, and the temperature of the alloy poured, light aluminum castings can be used unmodified sand over and over, while heavy cast iron castings will require significant make up binders to compensate for the burnt out binders


V/r HT1

 

That's almost a philosophical question for when gathered around the fire in your yurt:



( I have no idea but could not resist the temptation)

 

LOL, yes I see.

 

It's what HT1 said. You will develope the tests for your sand based on the success of your castings.
I use the same one for my petrobond. The squeeze test to see if it sticks to your hand (mud), then the break test to evaluate the tensile strength and clean separation. Then compare that to how well your patterns drew and the quality of the casting as far as surface finish or drops or inclusions or scabs or anything else that could be attributed to moisture. If I go with too much oil in the muller I can add drier petrobond to condition the mix. Green sand could be dealt with the same way, or just aireated.
This also applies to the lost foam mold. After vibration or tapping to settle the sand, stabbing straight down into the surface and seeing how far your fingers penetrate is an indication of how well the sand has compacted and then will hold its shape during the pour.

 

I own a run of the mill moisture meter, and doubt I'll ever break it out of the wrapping it came in, even if it's just to entertain myself with a green sand moisture check.

My ingredients were determined by a pro supplier so I'm going to have confidence in their ability to do their job, and base the amount of water I add on the 'hand ball' green strength test.

3% vs 4% or even 5%, I doubt will provide any difference in the quality of the finished product and/or go from a routine pour to a steam explosion.

Honestly... Who here would have a batch of dry-ish green sand in their muller (for example) and solely use a moisture meter to gauge its potential green strength and then would solely rely on that measurement to not only determine if they need to add water, but also do the math on the mass of sand in the muller at that given time, vs its current moisture content, to develop how much more water needs to be added...? I'm willing to wager that probably all of us would run the muller, grab a handful, determine it's too dry, and simply pump a spray bottle a few times into the sand, and run it for few minutes. Mix/repeat until the hand ball test meets our expectation.

Am I wrong...?

 

Hey..., I'm all for science. I'm curious how many follow the mathematic approach in practice though.

 

Resurrecting this thread as I had and experience molding that caused me to want to measure the moisture content of my sand. What happened was I rammed up my straight edge pattern and went to pull the cope and it promptly collapsed. This was a first for me and I was sure it was because I wondered if maybe my sand was a bit on the moist side for my previous mold. So, for this mold I decided to mull a little drier based on the “fist full of sand” squeeze test. Based on how little water added to a 3 or 4 gallon batch of sand it takes to go from too dry to just right, I suspected the actual moisture content difference would not be very great.

So, after the mold failure, I set aside a sample of the too dry sand and remulled 25 gallons of sand to “just right” (as if I truly know what is just right!). And I grabbed a pound of it and set it aside with each sample tightly wrapped in foil to maintain moisture content. When I got home I carefully weighed those samples and then cooked them at 350F for 3 hours and let them cool over night. It turns out the “too dry” sand had a moisture content of 15.5 and the “just right” sand was 17.4%.

The frustrating parts of this moisture content question are that the tolerances for a somewhat “touchy” pattern are pretty seemingly narrow and the squeeze test is very subjective. Perhaps with more experience I will be gain better reliability in determining the right mix. But right now it is a bit disturbing to realize how tough it seems to be get the mix right.

I’d be curious to hear what moisture contents others consider correct if anyone else feels like cooking a little of their green sand.

I did include a pic of the casting I am dealing with to provide an idea of the proportions of the pattern involved.
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