Whatever happened to kids' chemistry sets?
The first chemistry sets for children included dangerous substances like uranium dust and sodium cyanide, but all that has changed.
Talk to people of a certain age about chemistry sets and a nostalgic glaze comes over their eyes.
Stories of creating explosions in garden sheds and burning holes in tables are told and childhood is remembered as a mischievous adventure.
Portable chemistry sets were first used in the 18th Century but it took more than 100 years before they became popular with children, partly prompted by a desire to recreate the coloured puffs of smoke used by conjurors.
"It was part of a craze for what we call stage magic," says Salim Al-Gailani, historian of science at the University of Cambridge.
The early chemistry sets for children played on the idea of impressing school friends with a magic performance.
By the 1920s and 30s children had access to substances which would raise eyebrows in today's more safety-conscious times.
There were toxic ingredients in pesticides, as well as chemicals now used in bombs or considered likely to increase the risk of cancer. And most parents will not need to be told of the dangers of the sodium cyanide found in the interwar kits or the uranium dust present in the "nuclear" kits of the 1950s.
Most will know cyanide as a deadly poison, but one of its main applications is in gold mining. It can make gold dissolve into water.
Some chemistry sets of bygone ages even offered instructions and materials to be able to blow glass at high temperatures.
"You are letting a 12-year-old blow glass, there was uranium dust with a spinthariscope where you could see the radiation waves," says Rosie Cook, assistant curator at the Chemical Heritage Foundation.
"By today's standards, they're terribly dangerous but they're fascinating nonetheless."
Many distinguished scientists talk of how much influence their childhood chemistry set had.
Prof Mario Molina was a co-recipient of the Nobel Prize for his work researching CFCs' effect on the ozone layer.
"As a child I got fascinated with science," says Molina, who now heads the Center for Strategic Studies in Energy and the Environment in Mexico.
"What really started making a difference was starting to do things on my own, away from school, with chemistry sets, toy microscopes."
He then managed to turn a bathroom in his house into a chemical laboratory.
So what happened to the kits that were able to create the experiments that adults today so fondly remember? "Very often now, health and safety is used an excuse by schools, for example, not to do chemistry," says chemist Prof Martyn Poliakoff, of the University of Nottingham.
"Not that it's dangerous necessarily but it's cheaper not to do the experiments."
Chemistry sets started a sales decline in the 1970s, both Al-Gailani and Cook note. By the 1980s they had lost their mainstream appeal. But is it really a case of health and safety gone mad?
In the 1950s, booklets offered lists of instructions like "how to make an explosive mixture". Now, even mildly explosive chemicals have been removed.
Used often to test the presence of starch, the iodine solution once seen in kits is now regulated as a list I chemical in the US because of its use in the manufacture of methamphetamine. It can also be lethal if more than 2g of pure iodine is consumed.
Today's chemistry kits have a different emphasis. Some of the bigger sellers recently have included one capable of making edible creations tied to film franchises and a perfume kit aimed at girls.
These kits are not capable of the experiments of old.
"What used to be in chemistry sets that are not in there anymore are actual chemicals," says Cook.
"Given the right instruction booklet, the older set would allow the user to create all sorts of experiments - blow things up, create smoke bombs, create stink bombs."
Hiding away and experimenting is the thing that adults seem to remember most fondly about their childhood experiments.
"The nostalgia seems to be around the expectation of what could happen. The ability to use chemicals in free play meant going off recipe," says Cook.
"That has disappeared with the chemicals that have disappeared."
There's still excitement in some of today's kits. Potassium and sodium can be dropped in water to produce a violent reaction.
But in some, the emphasis is on everything from drinking straws and cardboard to ping-pong balls. Not quite the explosive mixture described 60 years ago.
"Most of them are what you could refer to as kitchen chemistry," says Cook. "Using things you can find in your kitchen - baking soda or vinegar."
Convincing children and parents that science is safe is a priority for health and safety executive chairwoman Judith Hackitt.
She showed, in an experiment for school children, that under very particular circumstances a fire could be lit and held in the hands. For science to move away from practical experiments because they are seen as dangerous, she believes, is a mistake.
"Yes they are safe. Are there some hazards associated with them? Yes, but of a very minor nature. The whole idea of them is you learn from handling real materials," she says.
The decline in the sale of kids' chemistry set was mirrored by a shift away from science as a career. Parents instead pushed their children towards finance, the law and the like.
But sales of kits are increasing again. Internet retailer Discover This reported strong sales for chemistry sets and microscopes in 2011. It said that parents were looking for toys with an educational value. Television shows focused on cool science - like US forensic science shows NCIS and CSI - have also had an effect.
At the same time, university application service Ucas has reported a 40% increase in the number of acceptances to chemistry courses at UK universities from 2003 to 2010.
And, with a little advice and supervision, the chemists of the future can play in relative safety.
"Don't lick it, don't eat it, don't sniff it, they are pretty good rules to live by in general," says Cook.