What do you do on a rainy day in Tassy? Why not visit the source of two of the island state's best known exports to the mainland: Boag's and Cascade beer?

Both rival breweries run public tours which show the processes of beer manufacture and conclude, inevitably, with a tasting session.

J Boag & Son's Centre for Beer Lovers is in Launceston, and more than 15,000 people toured it last year.

At the Cascade centre in South Hobart, visitor numbers increased last year to 30,000. Cascade Centre manager Paul Tickner says more people take the 75-minute tours on rainy days.

"They look out of their hotel window and if it's wet then they look at indoor attractions rather than those outdoors."

The Cascade brewery is Australia's oldest, founded in 1824 by Peter Degraves.

It is now a division of Fosters Australia, and it draws its water from the slopes of Mt Wellington.

Water source for Boag's is the Tamar Valley.

The original James Boag arrived in Australia in 1853 and after working for other breweries founded J Boag & Son in 1883. In 2000, it was bought by the San Miguel Corporation.

Boag sales and marketing director Lyndon Adams says the brewery tours "offer a rare insight into the beer making process, providing visitors with an experience that heightens their passion for beer. "Visitors enjoy being able to see and smell at first hand the liquid, as it is being transformed from raw materials to the finished product."

At the tour's formal tasting session in the Centre for Beer Lovers, guides describe each beer brand's appearance, aroma and character.

The centre is located in the restored Tamar Hotel, opposite the brewery, with 90-minute tours for up to 14 visitors available.

Cascade's tours for up to 16 people include a look inside the workings of the brewery as well as a walk through the nearby Woodstock Gardens and the Cascade museum.

At both brewery centres, visitors must comply with safety regulations, wearing flat covered shoes - not sandals; the tours are unsuitable for those with walking difficulties as some climbing is involved.

Further information: See discovertasmania.com.au.

- AAP