Melamine foam cleaning products. Also known as a magic sponge and magic eraser. Look out for the danger.

On the inside of my left arm, in the thin skin near the elbow is a rough-feeling red patch. It's been there for over a week. In the last few days it looked like a bruise. Before that it was like a graze without the blood. The surface of the skin was scaly. Before that it was like a superficial burn. Ane when I caused it, there was no pain at all.

What did I do?

I'd been painting. Some paint had dried on my hands, and there was a blob on my arm and it would not wash off. I'd been using a handy magic sponge to prepare a surface for painting, and it did a great job, so I figured it would get the paint off my hands. It worked ok. I scrubbed a bit and the paint came off. Then I used it on my arm and it did not really work well. Eventually I gave up and peeled the paint blob away.

About two hours later, a stinging red patch appeared. It hurt like a burn, so I put some anti-sceptic on it. That did not help. The stinging lasted for several days.

What had I done to myself?

Wikipedia tells us this stuff is formaldehyde-melamine-sodium bisulfite copolymer.

Those are big words, and I happen to know that formaldehyde is nasty stuff. It can exist in a gaseous state. It's been linked with cancer. At room temperature, it is a gas, smelly and colourless. So I wanted to know how safe it is in this commercially available cleaning-sponge.

Urea-formaldehyde is used in the glues that bond particle board together which is why you should always wear a quality gas-quality mask when cutting these products.

When reacted with melamine, formaldehyde produces melamine resin.

Had I given myself a chemical burn?

Being a skeptic, and knowing just enough chemistry to be careful, I looked further into this and discovered via snopes, that just because it mentions formaldehyde in the chemical composition, it does not automatically mean that it is chemically dangerous.

A classic example is that of sodium-chloride. This is just table salt, but neither the nasty sodium nor chloride is molecularly available while in this form.

So what is the painful patch on my skin? I conclude that it must be a mechanical abrasion.

I am relieved to learn that I have not been poisoned, or suffered an alergic reaction but still, there is a warning here.

These sponges are like very fine sand-paper. If you use one to clean off your toddler's face or delicate skin anywhere on an adult, then expect a nasty and long-lasting reaction.

It's a sponge, yet it acts like very fine sandpaper. In fact, the type of sponge is microscopically more like wire-wool than a typical kitchen sponge. It's what is called an 'open cell' structure which means that it is a nest-like structure. Therefore it is flexible, even though the filaments are rigid. The filaments are very hard, in fact almost as hard as glass. But they are also brittle which is why these sponges wear away quickly. However, the open cell structure traps dirt that is scratched off by the filaments, and the flexibility allows you to get into dips and curves.

You don't need to use soap or any chemicals - they work just with water as a lubricant, and they work very well.

You do need to be careful what kind of surface is being cleaned. If it is glass, then that's fine because glass is a little harder. If it is a rigid shiny plastic, then it is likely to take the shine off so try it first on a hidden area.

I find it excellent for removing marker-pen and crayon from walls, and for preparing generally sound painted surfaces for a touch-up or final coat.

Do not use it on your car.