The procedure of shell making goes as follows:
1. Immerse the cluster of wax moulds into the surface coating paint;
2. Lift the cluster, wrap with quartz sand with diameter 40-70 meshes and submerge it in the induration water consisting of Ammonium Chloride for 10-20 minutes;
3. Hang it for drying for about 40 minutes;
4. Immerse it into the reinforce coating paint;
5. Wrap it with rough sand with diameter 20-40 meshes and submerge it in the induration water made of Magnesium Chloride for more than 50 minutes;
6. Hang it for drying for not more than 30 minutes;
The 4th and 5th steps should be repeated several times to reinforce the shell until the sand shell is strong enough. Ammonium The concentration of Ammonium Chloride is 17%-22%. The 1.0-1.1 densimeter is used to measure the density once a week. Magnesium Chloride is used for the induration of reinforce layer. The density is 1.22-1.24. The 1.2-1.3 densimeter is used to measure the density every three days.