Silicate sodium

[l.mourad6663]

Hy  my friends my question

Is a certain concentration of sodium silicate solution required in the casting process?

[PeterH]

1 hour ago, l.mourad6663 said:

Hy  my friends my question

Is a certain concentration of sodium silicate solution required in the casting process?

First a brief statement of the pros and cons from
Understanding the Deflocculation Process in Slip Casting
https://tinyurl.com/2p96x33r

BTW https://digitalfire.com/ is a great site for background reading

So, it's a bit more complicated than simply adding x% of a deflocculant. For a given clay/water mix you are basically trying to add defloculant to achieve a low viscosity, while keeping safely away from the over-deflocculation ... and hoping that the result doesn't gel unacceptably.

A comprehensive process to do this from scratch is given in:
Determining Dispersant Additions for Casting Slips
https://tinyurl.com/34khjunr

Even if you don't do things this way it gives a clearer picture of what you are trying to achieve.

PS I understand that the modern polymer deflocculants (eg Darvan)  give superior results, are easier/more-foolproof to use, and damage the moulds less. While many sodium silicate based slips also benefit from the addition of soda-ash/sodium-carbonate. [Warning:  Darvan should be store above 10°C.]

[neilestrick]

I've attached a PDF with simple instructions for mixing casting slip. It's a good starting point. Every clay body behaves differently when deflocculating, so you'll have to make adjustments to get the specific gravity you want. Laguna Clay also has good instructions HERE.

Slip Mixing Instructions.pdf

[Min]

7 hours ago, l.mourad6663 said:

Is a certain concentration of sodium silicate solution required in the casting process?

If you use liquid sodium silicate (+ soda ash) from a ceramics supplier it should be the proper concentration. Concentration is measured in degrees Baume or Twaddle. 

(moving this thread over to Slip Casting section)

[Jeff Longtin]

Welcome to the Forum l.mourad6663. 

The simple answer, to your question, is Yes. The percent of "concentration" is the big question.

Are you mixing your own clay? Do you have a recipe you can post? If you're starting from scratch there will be a certain amount of trial and error to get the right percentage of sodium silicate. 

The actual percentage you use will be quite small, compared to the overall proportions of the entire mixture, but a little, one way or the other, will have a big impact.