GC EUROPE Fujivest Super - Manual (Page 14)

14
2.2 Mixing of the investment
In order to obtain a complete chemical reaction
between the powder and the liquid, it is important
to ensure that the components are mixed to a
homogeneous consistency.
- Pre-mix powder and liquid thoroughly by hand
with a spatula.
Be sure that all of the powder is completely
wetted by the liquid to produce a uniform
mixture.
- Mix for 60 sec under vacuum (320-420 rpm).
Always use a clean mixing bowl and check
the vacuum level. An inadequate vacuum
level leads to an inconsistent fit and casting
bubbles.
Insufficient mixing produces rougher casting
surfaces.
Faster mixing (and or longer mixing) accelerates
the set and decreases the working time and may
also result in lower expansion values.
Always check if the mixture is homogenous and
smooth with no dry ‘lumps’ before pouring the
investment.
Over time it is possible for a residue of investment
material to build up on the inner surfaces of the
mixing bowl and this can reduce the expansion, so
when switching to a new mixing bowl an increased
expansion may sometimes be noticed.
Tips for mixing:
- Use different mixing bowls for gypsum and for
phosphate-bonded investments!
Gypsum contamination interferes with setting
of phosphate-bonded investments.
- For efficient, homogeneous mixing, mix for only
one ring at a time.
- Check the mixing and vacuum efficiency.
Do not rely on the indicated vacuum levels on
the mixing devises.
- Use calibrated equipment.
- Change worn paddles or mixing bowls.
- To keep the mixing bowl, mixing paddle and
instruments clean:
Always clean them
immediately after use
eliminating all residues
of investment material
and store them in a clean
plastic container (the GC
Fujirock container makes
an excellent choice)
filled with water to help
reduce the risk of a build
up of sediment.