How to make soap

Soap making is a hazardous business. Frederika Whitehead braves a beginners' course and tries to avoid being burned, blinded or killed
soap making
How to make soap: add the dye slowly for a perfect soap (left) - rush it and you'll end up with the one on the right. Photograph: Frederika Whitehead for the Guardian Frederika Whitehead for the Guardian/Guardian

"Never put vinegar in your eyes and remember, the quickest way to kill someone is through the optic nerve straight to the brain," Sharon Homans warns.

Whoa. I'm glad I've come on a soap-making course: I've always been interested in the idea of making soap, but nervous about handling the ingredients. But the dangers posed by household vinegar hadn't even crossed my mind (soapmakers keep a bottle of vinegar handy to neutralise alkaline burns from the lye).

Some of my 25 fellow students have travelled to London from far-flung parts of the UK. The man on the door tells me people have flown in from Japan and Brazil before. The course is led by Melinda Coss, who is something of a grande dame in the soap world. She advises numerous cosmetics companies, and products devised by her are sold in Harrods as well as in the high street chain Lush.

Like Homans, Coss is refreshingly direct and doesn't waste words. She gives brisk directions about the soap-making process and then dispatches us into small groups to have a go at it ourselves.

Coss tells us that, in short, soap is a precise blend of the exact proportions of alkaline lye and acidic fat. The most dangerous ingredient is the lye, otherwise known as caustic soda. This lurks under the sink in most households for use as drain unblocker. If lye alone makes contact with the skin, it causes terrible burns.

My group is entrusted into the care of Homans, who seems intent on putting the fear of God into us. "Use very precise digital scales and don't ever deviate, not even by one gram," she says.

My group is tasked with making a lavender soap with blue and white swirls. When not warning us against putting vinegar in our eyes, Homans tells us the lye is out to get us. "It bounces," she says menacingly as one brave woman volunteers to measure it out. The rest of the group takes a big step back from the table in unison.

We're here to learn cold-process soap making, the method for making standard bars of solid soap. Elsewhere in the building people are learning how to make creams, lotions and liquid soaps, and how to comply with EU legislation.

Coss is excited today as she has recently learned a new shortcut that she is going to share with us.

In the past, home soapmakers heated the fat in one container while lye was added to water in another. When lye meets water it reacts dramatically, puffing out toxic smoke and heating up rapidly. Having melted the fat and dissolved the lye, the tricky bit was getting them both to the same temperature.

In the method that Coss has just come across, instead of using heat to melt the fat, the heat of the lye solution is used to dissolve the cold fat. This does away with the need for a heat supply and multiple thermometers.

Using the no-heat method, we make the soap using two plastic buckets. We measure the fat into one and the water into the other, add the lye to the water, and the lye solution to the bucket of fat. Apart from the need for precision measuring, it seems pretty non-technical.

Outside, Coss is making a goats' milk soap with her group. "As you are making it, it smells really horrible, but then it makes a really creamy soap and its lovely. Cow milk on the other hand makes a horrible soap," she says. As she adds the hot lye solution the heat burns the protein in the milk, turning it egg yolk yellow. "Can you smell it?", she asks the group. "It smells like pee."

Most of the people on the course are looking to get into the soap-making business. Jeanette Rennie, who came on the course with her husband, says: "We'd like to do it commercially, professionally, eventually, but we are going to start it as a hobby and see how it goes. I think it's nice, most of the stuff we've got at home in the kitchen so we haven't got to spend much."

Mark Nash runs Other Fish Ltd with his wife, and he too thinks soap making could be a viable business enterprise. "We make jams, chutneys, cheeses, so we are potentially looking at doing this as well. We've had one go at it so far. For our first batch we used suet and it was instantly disastrous. So our next go was with vegetable oil and that actually worked. It's a nice feeling, to make something that worked. We haven't scalded anyone and our fingers haven't fallen off."

Having mixed our soap and poured it into the moulds, we now have to wait six weeks for the acid and the alkali to neutralise one another. This process is called 'curing'.

The traditional way to test soap to see if it has cured is with the tongue. "If it bites, it's really not ready. If your tongue tingles, it's not ready. If it just tastes like soap, it's ready," says Coss.

So there we have it: soap licking. It's not something I ever expected to look forward to quite as much as I am.

More information on Melinda Coss's soap-making courses can be found at