I have no idea why anyone would want a wetting agent, apart from it's alleged benefits in potting composts.
What do you want it for?

If you must use one, get proper stuff

http://www.gardendirect.co.uk/index.php?main_page=advanced_search_result&search_in_description=1&keyword=wetting+agent&x=22&y=11

Surely it will rain soon enough, ours has gone green again in just a few days.

I'm totally puzzled too Scrumpyg. I can't see how adding pure soap to water is going to get the water any nearer the roots of the grass than just watering with a sprinkler - as Lizzie says it will rain soon enough.

Just water it with a sprinkler, you don't need a wetting agent for this purpose. Unless you're in the States and you're growing a particular type of grass, not sure where you are.

None of us is sure where Harry is Bamboo...

However if you are totally stuck on using one ecological washing up liquid should work as well as soap(But certainly no need for it on a lawn) All a wetting agent does is lower the surface tension of the water which is what soap and detergents etc do.

Hi to all who commented on my wetting agent question. I started to doubt my own reasoning after reading said comments, so, I went on line and came upon Lawnsmith,
looked at his lawn tips and he writes (quote)
Water Repellent Soil
Sometimes soil becomes very hard to re-wet once it has dried out. Even though this might be due to a fungal condition such as dry patch using a wetting agent* can aid water penetration and retention in most circumstances.
So I am back on my search for a DIY WETTING AGENT
Thanks to you all once again. Regards Harrybanana

Don't forget that the wetting agent is the final piece of the jigsaw.
If you have a serious problem with your lawn, cutting corners won't help.
Use the recommended products if I was you.

I agree that very hard, dried out soil can be tricky to wet again, but if you get yourself a lawn sprinkler, and leave it on for a few hours, it WILL wet your lawn and soak down to the roots, having said that I never water my lawn, because however dry and brown looking it gets, it will rain again eventually, {at least it will in the uk}, and your lawn will green up again in a few days.
As said previously, we don't know where in the world you are, if you could give us this information, it may help us to give you better advice, Derek.

1 can cola (not diet)
1 can beer (not light beer)
1/2 cup washing up liquid (not antibacterial)
1 cup ordinary household ammonia

mix in sprayer bottle that is on end of hose and spray on .