Scientists and Standards
Why do we need standards?
When baking a cake, it’s no good just putting flour, eggs and a few other bits and bobs into a pan and sticking it in the oven. You need certain amounts of certain ingredients, mixed and cooked in a certain way. Your best bet would be to follow a recipe.
Scientists have to follow recipes, too. They’re called standards, and you’ll find lots of them in the workplace. They provide precise instructions about how to carry out tasks, how to make things and how to test things.
Many industries create their own standards. Different chemical companies have different procedures for making a particular polymer, for example. But standards for testing the quality of raw materials and the performance of the polymer may well apply nationally or internationally.
The British Pharmacopoeia also applies nationally. It details specific ways of making up medicines.
The UK's - and the world's first - national standards body is the British Standards Institution (BSI).
So what is a British Standard?
The BSI describes a Standard as “an agreed way of doing something”. It may apply to a product, process or service.
But what does that mean?
Scientists need to follow standards to make sure the services they offer, or the materials and products they make, are safe and reliable. Things should be made or supplied to a certain standard.
For example, public health laboratories test food and drink samples in specific ways. There are, among others, British Standards for analysing ice cream, testing water quality, and determining the bacterial content of milk.
So British Standards are used everywhere?
Many things you buy or use will have been made to British Standards. For example, if you buy an electrical appliance, the ‘standard’ plug will fit into a ‘standard’ socket, sending a current down a ‘standard’ wire, and it won’t cause a fire when you switch it on.
What does a British Standard document look like?
All standards need to be clear and unambiguous. Those that deal with different kinds of method (for example methods of analysis or methods of evaluating performance) are not all the same, but look similar. Many of the standards for testing properties of materials have eight or more headings. Let's look at some of these headings in more detail:
1. Scope
This tells you what the test procedure can be used for. For example, BS EN ISO 10545-5:1998 (a British, European and international standard for testing the impact resistance of ceramic tiles) says:
"This part of BS EN ISO 10545 specifies a test method for determining the impact resistance of ceramic tiles by measuring the coefficient of restitution".
Note: BS EN ISO 10545 is a European and international standard that has been adopted as a British Standard.
2. Principle
This tells you the scientific principle on which the standard is based. BS EN 1936:1999 (a British Standard for testing the density of natural stone) says:
"After drying to constant mass, the apparent density and the open porosity are determined by vacuum assisted water absorption and submerged weighing of specimens. The real density and the total porosity require the specimen to be pulverized".
You'll notice quite a few technical terms (what's "apparent density"? for example). That's why British Standards also have a section called definitions.
Note: BS EN 1936 is a European Standard that has been adopted as a British Standard.
3. Definitions
This describes many of the terms used in the test, to avoid any doubt. For example, in the Principle above, the term "apparent density" is used. This is defined as:
"Apparent density (rb) the ratio between the mass of the dry specimen and its apparent volume"
And yes, you've guessed it, there's also a definition given for "apparent volume"!
4. Symbols
This tells you the exact meaning of any symbols used, for example:
"(rb) the real density of the specimen, in kilograms per cubic metre"
5. Apparatus
This tells you all the equipment you'll need to carry out the test.
6. Test Specimens
In some tests, the test specimen (in other words, the object you are testing) has to be a certain size or shape. It may also have to be prepared in some way. This section also tells you how many specimens you should test. (Slight variations and differences can happen when you test more than one specimen, so we should repeat experiments to be sure of our results; in other words, check their reliability.) If we look at BS EN ISO 10545-5:1998, we see an example of this:
"A minimum of five test pieces in dimensions 75 mm x 75 mm cut from five tiles. Tiles with fixed dimensions less than 75 mm may be used"
7. Test Procedure
This tells you the procedure you must follow: it tells you what you have to do. Sometimes there are diagrams to help you.
8. Expression of Results
This section tells you how you should write your results, and gives you the formulae for any calculations you have to carry out. It also tells you what units to use. For example, in BS 2782-3 (a British Standard for testing impact resistance of plastic), the following equation is given:
S = (v0 - p/3m) x t
where,
m is the falling mass, in kilograms
v0 is the impact velocity just before impact, in metres per second
t is the time to peak force or the time to failure, in seconds
p is the impulse imparted up to the time of occurrence of the peak force or up to the time of failure, in newton seconds
9. Test Report
This final part outlines what you have to write in your report. BS EN ISO 10545-5:1998, for example, says:
The test report shall include the following information:
(a) a reference to this part of BS EN ISO 10545;
(b) a description of the tiles;
(c) the coefficient of restitution of each of the five test specimens tiles;
(d) the average coefficient of restitution;
(e) any indentation or cracking of test specimens.
Why do standards need to have so much detailed information?
If you’re making or testing something to within a British Standard you have to do it in exactly the same way as someone else making or testing the same product. If one of you did something differently, the product or test results would be different. That’s why instructions in a standard have to be really precise.
Have a look at these instructions from a packet of washing powder:
| Water hardness | Soiling | ||
|---|---|---|---|
| Light | Normal | Heavy | |
| Soft | 80 ml | 110 ml | 150 ml |
| Medium | 100 ml | 130 ml | 170 ml |
| Hard | 130 ml | 160 ml | 200 ml |
- Measure the correct amount of powder into the machine, according to soiling and hardness of water. See table for amounts.
- Follow garment manufacturer’s instructions.
- Use the lowest recommended temperature.
It’s fairly straightforward if you just want to wash your smalls. But what if you wanted a whole group of people from across the county to perform consumer tests on washing powders? The above instructions wouldn’t be precise enough. Some of the terms are ambiguous. In other words, some people might interpret them differently. For example:
Size of washing machine: it doesn’t say how much water the powder should be dissolved in; bigger machines hold more water.
Water hardness: Does ‘soft’ mean no hardness at all? How much hardness makes water ‘hard’? And how hard is ‘medium’?
Soiling: how much dirt counts as ‘normal’ soiling? Does the type of soiling matter? Is a blood stain worse than a grass stain? Does ‘heavy’ soiling mean lots of small stains or a few large stains?
Temperature: the recommended temperature depends on the type of garment. One of you might wash a T-shirt at 40oC, while another washes their pants at 60oC. The washing powder is likely to perform differently at each temperature.
More information about British Standards and BSI. [link to http://www.bsieducation.org/Education/14-19/about/default.shtml]