still learning, what causes this texture

[GreenTwin]

780 C = 1,436 F

The lower temperature pours seem to give a shinier smoother finish, and the higher temperature pours give a more dull coarse finish; that has been my experience.

Since your pours are shiny, I think your pour temperature is good, and I agree with McKee about the sand probably being the culprit.

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[ddmckee54]

GreenTwin, thanks..... but I think you probably meant DaleW. He was talking about the sand, I was just talking about the IR gun.

 

[GreenTwin]

LOL, I am not sure who I am referring to.........just blogging along until the third cup of coffee (tall glass actually, a cup just does not cut it) kicks in.......

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[werowance]

ill go along with not pounding that new sand hard enough for one thing. where i took a brass tube to vent the center of the wheel - that area came out smoothe as a a babys butt. when it hit the wheel form the texture was not. i mean it was much better with this new finer grain sand the ok85 i think was the number - but where i packed it around the form i think must have needed to be harder. the pushing the tube thru to vent the sand and the movement of it i think packed it harder there and that was the smoothe part. i didnt get a photo of it before i cut it off. next session ill try to pack the crap out of it and see what i get. also took a visit to my moms shut down potery business. clinch mountain pottery. she had large gas fired kilns. one was run on railroad track and the hood moved over the stacked unfired pottery and the doors shut down over it. bigger than my full size truck. she had a few pyrometers laying around. old analog ones with long leads with that white wire wrap around it. i didnt get a chance to talk to her about them but thinking of seeing if i can procure one of those and see what i can come up with.

 

[GreenTwin]

What sort of sand/clay mixture ratio are you using ?
And, if the sand is not mulled (mixed) well, you can have pockets of high/low clay content, which can affect surface finish.

myfordboy mulls his sand on the floor (requires good knees).
You can fold the tarp over the sand, and just walk around on the sand, turning the sand over, and walking, to mull it.

Edit:
The process of mulling greensand (with a mechanical muller) smears the sand and clay together, and then breaks the sand up, doing what I call "fluffing" the sand. Fluffed greensand can be compacted in the mold; non-fluffed greensand does not compact very well.

Bound sand does not work the same way.
There is no clay in bound sand; it is only sand and binder (resin or sodium silicate).
If you try to do much compacting with bound sand, you end up fracturing the sand, and causing it to shift away from the pattern and crack.
Bound sand is pressed into place tightly around the pattern, first with the fingers, then with the heels of the hands.

 

[werowance]

What sort of sand/clay mixture ratio are you using ?
And, if the sand is not mulled (mixed) well, you can have pockets of high/low clay content, which can affect surface finish.

myfordboy mulls his sand on the floor (requires good knees).
You can fold the tarp over the sand, and just walk around on the sand, turning the sand over, and walking, to mull it.

Edit:
The process of mulling greensand (with a mechanical muller) smears the sand and clay together, and then breaks the sand up, doing what I call "fluffing" the sand. Fluffed greensand can be compacted in the mold; non-fluffed greensand does not compact very well.

Bound sand does not work the same way.
There is no clay in bound sand; it is only sand and binder (resin or sodium silicate).
If you try to do much compacting with bound sand, you end up fracturing the sand, and causing it to shift away from the pattern and crack.
Bound sand is pressed into place tightly around the pattern, first with the fingers, then with the heels of the hands.

70%sand 30%clay by volume. measuring it out in pint jars. i hand mull it taking hand fulls and rubbing both hands together and letting it fall back in the batch. i use a very large pan to do it in. my fingers and hands cramp up and it definately will wear down some skin along the way. doing it in small batches of 7 pints sand and 3 pints of clay at a time. a small batch usually takes a few afternoons of my time after work before i figure its good enough

 

[ddmckee54]

I think for the initial mixing of the green sand you pretty much have to beat the crap out of it. (Or more precisely, beat the clay onto the sand.) I remember tales from years ago on Alloy Avenue, guys would cover the sand/clay mix with a tarp then drive over the tarp with their car, fold the sand over, and repeat - until all the sand was thoroughly coated with clay. If you have close neighbors they just might question your sanity, driving back and forth over a pile of sand.... But hey, if it works that's all that counts.

 

[werowance]

well, i can certainly put it on a tarp and do this. i have rammed 2 test molds without a pour and 2 test molds both with aluminum pours (discarded the burnt sand each time) but definately cant hurt to ram it more with the truck. probably better that way that sanding the skin off my hands any how

 

[werowance]

also this will hopefully be my next pour - the cho cho stack to go along with those 2 wheels i cast. below is how i plan to do the mold. is this ok? rough hand drawing with poor diminsions but hopefully close enough to represent the plan. what do you think of this setup for the mold? would it need a small vent somewhere in the middle of the stack?