Guest spot Got to be white by Andre Farley

A view of silos based on experience . Mr Farley is in the business of sealing and waterproofing silos. He writes:

"If you are in the market for a sealed silo this year, make sure you buy a white one. In my opinion, after eight years experience sealing silos, unpainted ones are unsatisfactory.

In a white silo, freshly harvested grain can be stored at a lower temperature and the need for aeration, if any, will be reduced.

In a non-white silo, on those hot, post-harvest days, the residual moisture in the grain is condensing on the silo ceiling as well as being expelled through the pressure relief valve. At night as the silo and grain cool, it sucks air back in — moist night air. This continues for months and a lot of farmers find that they have a crust — 50-100 mm of black crusty grain. This won't happen in a white silo because the temperature variation is minimised.

Critical temperatures for grain are as follows: grain for seed, oilseeds and malting barley, 43°C; food grains, 54°C (figures NSW Agriculture). The seed will handle these temperatures, but not day after day. The ones that will be damaged are the seeds closest to walls and roof of the silo.

The air temperature inside an unpainted, unsealed 140 (tonne) bag silo was 45°C on a clear and sunny 32°C day. The next day — 36°C — inside (the silo) was 56°C. The same silo, after I sealed it and painted it white, tested at 30°C inside on a day when the outside temperature was 29°.

If you fumigate for weevils in a sealed silo you need to keep the gas in for the recommended time, not being expelled all day then being replaced by fresh air at night.

A farmer I spoke to at a field day described his unpainted, sealed silo, next to which he happened to be working on a hot day with intermittent cloud cover, as "working like a bellows." Every time the clouds went in front of the sun the silo would suck in, and when they blew past, it would expel again. Anybody who has shovelled and swept out an old flat-bottom type of silo will attest to how hot they are inside.

So when pricing your next sealed silo insist on a white one. Also ask to have a pressure test after delivery. I've seen some examples of sealed silos in the factory which are a long way from sealed by the time they are laid down on the trailer, bounced and bumped all the way to your place, and stood up again.

A high gloss paint with a UV protection is the longest lasting paint."