GC EUROPE Fujivest Super - Manual (Page 7)

7
Focus Edition from GC
1.3 Working temperature
The working temperature of the investment powder
and liquid are critical factors in determining the
setting time, expansion, surface roughness and
consequently the final fit of the castings.
The optimal working temperature of both powder
& liquid is 21-23°C, this must be considered if
either the room temperature is lower than this
or the materials have been stored at a lower
temperature.
If the ambient working temperature is below
20°C, the following problems can occur:
- A delay in setting time
- Uncontrollable expansion values
- A reduced surface quality, meaning a rougher
surface of the casting object
- A higher risk of crack formation leading to
possible miscasting
Likewise if the ambient working temperature is
higher than 21-23°C the following factors must be
considered:
- An increase in temperature of liquid and/or
powder decreases the working time and
accelerates setting
- The working time at 23°C is approximately
9 min, whilst at 24°C it will be approximately
8 min as for each 1°C increase in working
temperature the working time decreases by
+/- 1 min
- If the temperature of the powder and liquid
cannot be optimised a slight reduction in the
mixing time may help increase the working
time
The use of a temperature controlled refrigerator
set at 21-23°C is highly recommended for the
storage of the investment powder, liquid and
mixing vessels, as this completely eliminates the
risk of seasonal temperature differences.
1.4 Preparations before investing
1.4.1 Modeling
- Die Separator
Use a high quality type 4 dental stone such as
GC Fujirock EP for optimal accuracy and wear
resistance. GC Multi Sep is an ideal wax separator,
leaving no oily residue on the die stone surface.
- Modeling materials
The correct positioning of the wax/resin patterns is
important in order to ensure sufficient thickness of
investment material around the objects to withstand
the casting forces and provide sufficient expansion.
The highest point of the pattern structure should
be 5-10 mm lower than top of the ring and at least
5 mm away from the axial wall of investment ring.