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INVESTMENT CASTING
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Investment casting also known as Lost Wax Process is widely used for making intricately shaped
components. This is also the predominant process used in the jewelry sector. Wax patterns,
identical to intended part require finishing before being used for further processing.
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CTC is generally used in jewelry casting to eliminate dimensional irregularities and appearance
of parting lines. Another important use of CTC in jewelery casting is for finishing of re-sized
wax patterns. Since to produce multiple sizes for each pattern is expensive, the standard patterns
are cut to required sizes, joined and subsequently finished using solvents. CTC is applied to wax
patterns using brushes or cotton swabs to impart smooth surface finish of the wax patterns.
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POSSIBLE ALTERNATIVES TO CTC
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The table below presents a list of possible alternatives to CTC for finishing wax patterns in
Jewelry sector; some of the solvents have already been adopted by the industry with satisfaction
and others are identified by GTZ through trials with a specially designed test procedure.
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| Parameters |
Flash Point
oC |
Boiling Point
oC |
Vapour pressure
mmHg |
Dipole moment
Debye |
Hansen
solubility
parameter |
| Acetone |
-20 |
56 |
180 |
2.9 |
20.0 |
| Isopropyl alcohol |
12 |
82 |
33 |
1.7 |
23.5 |
| Perchloro ethylene |
None |
121 |
14 |
0 |
20.3 |
| Toluene |
4-7 |
111 |
21 |
0.3 |
18.2 |
| Xylene |
38 |
138 |
6-16 |
0.6 |
18.0 |
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HAZARDS TO CONSIDER
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No alternative solvent to CTC can be regarded as an ideal substitution. Each substitute has limitations specifically
from the point of health and safety. While most solvents are toxic, the degree to which they are toxic may vary from one
to the other. Understanding the strengths and weaknesses of alternative is essential for taking informed decisions.
In the context of jewellery casting, the risks associated with flammability, inhalation, skin contact and ingestion
needs to be considered.Click
here to review the key to the hazard
categories. The table shows the ratings for each hazard category on a comparative scale.
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| Substance |
Risk Categories Evaluated |
| Inhalation |
Skin |
Environment |
Flammability |
| Water |
None |
None |
Not Classified |
Non-flammable |
| Acetone |
Irritant |
Irritant |
Not Classified |
Highly flammable |
| Isopropyl Alcohol (IPA) |
Irritant |
None |
Not Classified |
Highly flammable |
| Xylene |
Harmful |
Harmful |
Not Classified |
Flammable |
| Toluene |
Very Toxic |
Toxic |
Not Classified |
Highly flammable |
| Perchloro-ethylene (PCE) |
Very Toxic |
Toxic |
Very hazardous |
Non-flammable |
| Carbon Tetrachloride (CTC) |
Very Toxic |
Toxic |
Very hazardous |
Non-flammable |
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FURTHER INFORMATION
Further tests on safety aspects such as exposure limit are being carried out.
A detailed technical document titled "Selection and Safe Use of Alternatives to CTC- Investment Casting Process"
will be published and distributed to affected industries. The same can also be downloaded from this web site soon.
Comments? Questions? Suggestions? Please
click
here to let us know!
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Disclaimer
Ü Though all care
has been taken while researching and compiling the information presented
above, GTZ Proklima accepts no liability for its accuracy. The reader is
advised to confirm its correctness prior to use or purchase of any substance.
Ü GTZ Proklima
makes no claim in respect of the suitability of any substance as substitute
for CTC in any specific industrial process. Suitability remains to be verified
through trials with due consideration of health and safety aspects.
Ü Information provided here
does not constitute an endorsement or recommendation of any product by GTZ
Proklima. While preference is given to non-proprietary products information on
selected proprietary products may be included if they appear to have a better
environment, health and safety performance or if they are already widely
adopted by the industry.
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