When buying a vacuum flask, we generally decide on whether to buy it or not by its size, look and price. Next comes the question of whether it can keep the liquid stored in it hot or cold. However, only when you use the flask do you start experiencing problems. For instance, leakage is one problem. The bad odour in the flask absorbed by the liquid stored in it is yet another problem, which happens primarily because of the manufacturing defect of the flask’s cap.

The huge range of branded flasks prompted Consumer Education and Research Society (CERS), Ahmedabad, to test 31 models of vacuum flasks against a series of parameters like heat and cold retention capacity, leakage and more.

A health concern

If a flask cannot retain the heat of a liquid stored, it is useless. Similarly, if it cannot retain the coolness, how can fruit juices, cold coffee and so on be stored in it? The quality of stainless steel and plastic used in the manufacture of a flask and the mouth (stopper or cap) of the flask is another area of concern because poor colour and plastic result in the leaking of harmful chemicals.

CERS tested the brand, High Grade Vacuum Flask. It claimed to have 18 by 8 quality steel but it had already begun to rust from the inside after a brief period of use. What is dangerous is that this rust may easily contaminate the liquid stored in a flask.

No regulations

An interesting fact is that though vacuum flasks have been in the Indian market for at least five decades now, and the stainless steel variety for the past two decades, the Bureau of Indian Standards (BIS) has neither laid down standards for stainless steel vacuum flasks nor is there any mention of the authority which governs the manufacture and sale of vacuum flasks — glass or steel. As of now, in the absence of any regulatory authority, anyone can manufacture, sell, import or export vacuum flasks. Doesn’t this indicate the poor regulatory framework in our country?

The volume — claimed and actually found — was another surprise. The High Grade Vacuum Flask, claiming to have a capacity of 500 ml, contained only 160 ml of liquid and the same brand claiming one litre of volume capacity held only 370 ml.

Mayur Café could not retain the heat of the liquid. It retained only 76°C and 48°C against the standards that require 88°C and 70°C after one hour and five hours, respectively. High Grade Vacuum Flask (500 ml) held only 69°C and 42°C.

Volume

We usually buy a vacuum flask keeping in mind its capacity (volume) and assuming that what the manufacturers claim is true. But three brands failed the CERS test. The brands claimed to hold far more than they actually did.

High Grade Vacuum Flask, the worst of the three, claimed 500 ml and 1,000 ml but actually held 160 ml and 370 ml, respectively. Maxim and Gangzida claimed 1,000 ml but held 930 ml.

The standards specify that vacuum flasks should have a volume of 250 ml, 500 ml, 750 ml, 1,000 ml or 1,500 ml. But CERS found brands with claims of 600 ml and 1,200 ml. Cello Senorita, Milton Thermosteel and Freelance claimed 600 ml capacity and another model of the Freelance brand claimed 1,200 ml.

Heat holding

One of the main uses of a vacuum flask is to retain heat. High Grade Vacuum Flask (1,000 ml and 500 ml), Eagle Shell Jupiter, Cello Pluto, Milton Ellie and Jaypee Stellar, all of these 1,000 ml, Milton Thermosteel (600 ml) and Mayur Café (500 ml) failed this test.

The temperature in both Milton models that failed the test should have been at least 70°C after five hours but was only 60°C in the case of Milton Ellie and 65°C in Milton Thermosteel (600 ml). High Grade Vacuum Flask (1,000 ml and 500 ml) failed in the first hour itself. So if you want to keep liquids hot, don’t go for these models.

Leakage

CERS’ test for leakage was to inform consumers about the models that leak. High Grade Vacuum Flask, both 500 and 1,000 ml, and Cello Pluto (1,000 ml) and Mayur Café (500 ml) leaked.

Coolness holding

As there are no standards laid down by the BIS for coolness, CERS formulated its own. Milton Ellie, Cello Pluto, Jaypee Stellar, Eagle Shell Jupiter, Padmini Champ (all 1,000 ml), High Grade Vacuum Flask (1,000 and 500 ml), Milton Thermosteel and Freelance (600 ml) and Maxim and Mayur Café (500 ml) failed this test. The temperature of the liquids stored in High Grade Vacuum Flask (1,000 ml and 500 ml) were 24°C and 27°C, respectively, when it should not have been more than 12°C. The liquid in Mayur Café (500 ml) had a temperature of 23°C.

Sensory analysis

We often find that the taste of a liquid stored in a vacuum flask, whether it is tea, coffee or juice, changes after being stored for some time. CERS therefore conducted sensory tests on six randomly selected models and found that most of the panellists liked the tea stored in Milton Ellie, Prestige, Nissan Picasso and Freelance during the first two tests. In the third test, black tea was stored in the flask. Milk was added only before serving. When the panellists of the third test were asked to compare the taste with the fresh tea, Milton Ellie and Blueplast Steel Vac were preferred.

Manufacturers’ response

As a policy, CERS conveys all test results to manufacturers. All manufacturers receive the results of their own product only and are given two weeks from the date of receipt to respond.

Nissan contended that though plastic houseware does not come under any regulation in India, it had its own internal quality control techniques, developed over the years. The colours used in the flask such as white and pearl colours cannot be used in recycled polymer. That the material is virgin can also be verified by chemically testing the product.

On the retention of odour, Nissan said that vacuum flasks were like glass containers. If you keep items with very strong smells like coffee or tea in them, they will retain the odour, unless washed properly with warm water and kept open for airing till the smell goes off. This is true of glass as a material as much as it holds true for a glass flask.

Insight

If vacuum flasks do not come under any regulation, who ensures that they are manufactured as per the standards? If the manufacturers provide substandard flasks, whom does a consumer approach?

Prestige responded by saying that they stopped selling these flasks at least two years back and hence these tests had no relevance for Prestige stainless flasks anymore.

CERS purchased the models in July 2007. If Prestige stopped selling them two years ago, how were they available in the market? If they are still available, the test has relevance to consumers.

The manufacturers of Cello, Milton, Blueplast, Maxim, Emel Lord, Cosmic, Freelance, Gangzida, Premium Bottle, Jaypee Stellar, High Grade Vacuum Flask, Eagle, Mayur Café and Padmini Champ did not respond till the time of going to press.

For more information write to cerc@cercindia.org