Casting question.

[bigegg]

I've been watching this:

at around 3.20 onwards, cement powder is sprinkled and spread over what will become the inner surface of a cast aluminium pot.
I've done some research, and I can't find a reason this would be done.
It's not been used as parting powder, as it's applied after the pattern is removed,
not to strengthen the mold (randupson process [1])
I'm guessing it's just to improve the surface finish of the inside of the finished article, but I'm wondering if it perhaps forms a protective layer (to protect the aluminium from acidic food?)
Does anyone know???

https://books.google.co.uk/books?id...AEwAg#v=onepage&q=molding sand cement&f=false
[1] http://www.submarineboat.com/casting_boat_props.htm
Tool and Manufacturing Engineers Handbook

 

[cumbriasteve]

From what I can see it's for finishing reasons, the cement powder is finer than the sand so can be smoothed down to a higher degree, I doubt it leaves any benefit coating to the aluminium.

 

[CRB]

From what I can see it's for finishing reasons, the cement powder is finer than the sand so can be smoothed down to a higher degree, I doubt it leaves any benefit coating to the aluminium.

I thought that too, but do not know enough to begin with.

 

[bigegg]

I've asked the question on a chemistry forum, but since it's only early morning in the US, I doubt i'll have an answer before tomorrow

 

[cumbriasteve]

I thought that too, but do not know enough to begin with.

You can't know less than me about casting , so I am more than prepared for my guess to be proven wrong.

 

[bigegg]

I know enough to be dangerous

I've got a job in the next couple of weeks to do a cast aluminium hand for a 1st birthday present.
I'll be taking photos and maybe write up a "how-to"

 

[CRB]

Going back a little BigEgg....?What happened with the Princess Castle?

Sounds like you get all the good jobs

 

[bigegg]

Going back a little BigEgg....?What happened with the Princess Castle?

Sounds like you get all the good jobs

Best price i could get for cardboard tube was £110!!!!

Went to mothercare, and bought a BIG wooden dollhouse for £60 instead.

 

[Robotstar5]

I did my apprenticeship in an iron foundry and remember them shaking a bag of white powder onto the 2 halves of the mould before they closed it for casting, no idea what it was for though.

 

[Rocketman]

I did my apprenticeship in an iron foundry and remember them shaking a bag of white powder onto the 2 halves of the mould before they closed it for casting, no idea what it was for though.

In that case it sounds like a release agent I would guess.

 

[bigegg]

In that case it sounds like a release agent I would guess.

parting powder (or release agent).
I use asda smart price talculm powder

 

[brightspark]

I did my apprenticeship in an iron foundry and remember them shaking a bag of white powder onto the 2 halves of the mould before they closed it for casting, no idea what it was for though.

parting powder

 

[Wendelspanswick]

Having watched the video I guess that they have a very limited supply of resources so cement is used (a fairly common resource) to give a finer surface finish on the casting.

 

[DanielW]

I've asked the question on a chemistry forum, but since it's only early morning in the US, I doubt i'll have an answer before tomorrow

you know this is a third world country in the vid,I guess if they could get their hands on talcum powder they'd be using it on their feet rather than wasting it on sandcastings.

 

[evobilly666]

Sure when I watched it the other day the bloke said it was to give a better finish. It was then smoothed with a wet spoon

 

[bigegg]

Sure when I watched it the other day the bloke said it was to give a better finish. It was then smoothed with a wet spoon

so he did - I don't normally put the sound on youtube - usually irritating soundtracks, and worse presenters