Pink trails of retardant were strewn across the road, south of Tharwa, in a desperate attempt to beat the clock as the fire crept into the land.

The Namadgi Visitor Centre was covered in the sticky pink substance, as were properties, roads and farmland.

The visitor centre is at the base of Mount Tennent, where the fire has gradually climbed over since it started.

Naas Road was clear, except for the occasional resident, fire truck or police car.

This was clearly an air mission as the fire burned deep within rugged terrain, hard to reach by both foot and road.

Helicopters roared above, constantly filling water from whatever water sources they could find and then dumping it in a hope to choke the oxygen out of the beast.

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Saturday evening was a crucial point for crews who had contended with horror fire - with warm weather and winds exacerbating the flames.

Prior to Saturday there were grave fears for Tharwa Village and its small populace. A fire spread prediction map, released on Friday, had the Orroral Valley fire going straight through the town.

But as of Saturday evening, the fire was burning more than two kilometres south of the township. The Emergency Services Agency described it as "a good firefighting day".

Extraordinary stories of calm defiance under severe threat emerged from the properties in the direct line of fire.

Caloola Farm on Top Naas Road was boxed in on three sides by fire, said Ralph Hurst-Meyers, who runs it.

Three of his workers stayed and manned fire trucks they had constructed themselves by putting 1000-litre tanks and petrol-driven pumps on the back of vehicles.

"They have been taking out the spot fires," Mr Hurst-Meyers said.

At one stage the farm, which doubles as a conference centre, looked doomed but the three workers held the fire back long enough for fire retardant to be laid.

"They sent in a jet water bomber and it laid a line of retardant," the owner said.

Eight Rural Fire Service trucks also arrived and Mr Hurst-Meyers had nothing but praise for them.

He said his centre also had 120,000 litres in reserve which he said neighbours were free to use.

But the RFS has been very active protecting the property. "They sent in a jet water bomber. They've laid a line of fire retardant," he said, adding eight RFS fire trucks on the ground had also been in action.

Another rural property owner said the fire had slowed down as the wind changed.

"It hasn't gone away," Jennifer Filmer said. But it hadn't hit as they feared it would.

She and her husband, Pete, were braced for fire from the day before. On Saturday, they were watching it approach.

They could see the Mount Tennent fire from the top of the ridge above their property so they and other members of the family took turns as look-outs on the high ground, changing the guard every 15 minutes because of the heat.

They were monitoring the colour of the smoke. On late Saturday afternoon, Ms Filmer said the smoke was pale in colour, indicating it was coming off a low fuel area. Dark smoke over the farm meant the fire was more threatening.