[TheForge] Strengthening castable refractory

[Thomas A. Troszak]

 > Subject: Re: [TheForge] Strengthening castable refractory
> From: Marc Godbout <marc@ironringforge.com>
> Date: 26 Aug 2003 20:14:30 -0500

> Water for casting: Approx. 55% by weight
> 
> Now a question. The best way to prevent checking is to use the minimal
> amount of water. They give an approximate amount, 55%, but how do I tell
> when it's enough? From what I've read on other mixes, it should be just
> enough to hold it together when clumping it in your hand. Does that

Dear Marc,

From my experience with other brands, about 10 lbs. water per 20 lbs. dry,
or the wet mix is about 1/3 water by weight. This varies with the type,
though. Start with the manufacturers recommendation, but don't add it all at
once, if you get the right consistency and still have water left, no
problem.

I usually weigh out the maximum amount of water estimated into a bucket,
then add only about 3/4 of it to the dry powder all at once and mix
THOROUGHLY and quickly until all the particles are wet, and add the
remainder of the water a small bit at a time just until the mix is the right
consistency.

The wet mix should be stiff enough to stay heaped, (like making a sand
castle) and not flow down by itself. If you are trying to fill a form, make
it just wet enough to heap up, but still "settle" when the form is tapped
lightly. if you are just ramming it into a box, it can be drier. I use a
needle scaler or auto body hammer to buzzz the form to get the relatively
dry mix to flow down into the corners, or just tap it with whatever is
handy.

By the way, that stuff starts to set in about 20 minutes whether you are
done or not, so mix fast!

Tom Troszak