The eco-friendly Ganpati conversation has been running for two decades and has mostly been framed as a moral one. It is simpler than that: it is a question of what the idol is made of, and what that material does once it is in the water.
What actually happens in the water
Shadu mati is river clay. Put it in water and it breaks down within hours, which is precisely what an immersion is meant to represent.
Plaster of Paris is calcium sulphate hemihydrate. It is cheap, light, and takes fine detail, which is why idol makers moved to it — and it is close to insoluble. POP idols recovered from tanks after a season are often still recognisable. The paints are the second problem: bright synthetic colours on POP idols have repeatedly been found to carry heavy metals, which do not leave the water afterwards.
Telling them apart at the shop
Sellers are not always forthcoming, and "eco-friendly" on a sticker means nothing on its own. Two reliable tests:
- Weight. Clay is much heavier than POP. Lift two idols of the same size and the difference is obvious immediately.
- Finish. POP takes very fine, sharp detail and a glossy paint finish. Shadu mati is softer-edged, and is usually finished in natural or muted colours.
- Price. A genuine clay idol costs more, because it is heavier to transport and more of them break in transit.
Immersing at home
For a small shadu mati murti, a home visarjan is straightforward and is what many households in flats now do. Fill a bucket or a large steel vessel with water, perform the final aarti and naivedya as usual, and lower the idol in. A clay murti will dissolve over several hours; leaving it overnight is normal.
The water afterwards is used on plants rather than poured down a drain, which is where the practice gets its name — visarjan into the earth rather than into a tank.
A word of caution: this works for clay. Do not attempt it with a POP idol, which will simply sit in the bucket, and do not do it with a large murti.
If you are using a municipal tank
Most corporations in Maharashtra now place artificial immersion tanks across the city during the festival, and several have moved to restrict POP idols in natural water bodies. Locations change every year and are published shortly before the festival — find your nearest one before visarjan day rather than on it, when every route into the city is diverted.