After decades of playing around contriving formulas for messy concoctions, and trying to do it on a budget, I've stumbled upon a great formula...
You need a good-sized blender, something for making smoothies or whipping up recipes in the kitchen, preferably very powerful and the bigger the better.
Fill about 2/3 full with water. Squirt in water-based paint as a tint if desired. (dollar stores carry it) While running on low, add about a tablespoon of 'Yuck' powder and let it continue mixing for half a minute. Next, add dishwashing liquid, preferably the brand in the picture, as it works best. Squeeze in about five times the amount you'd use to do the dishes. Lastly, slowly and carefully pour a couple of tablespoons of Zanthan Gum in WHILE THE MACHINE IS RUNNING. It is important that this powder is mixed immediately so that it doesn't form lumps. After a very short while, you should hear the machine slow down a bit, as the mixture will get very thick very fast.
You don't need to mix it for long, half a minute for each ingredient is enough in my case, though other blenders may run differently.
Next, pour the whole contents into a large bucket. Using a paint-stirrer attachment on a drill, begin further mixing the stuff while adding water slowly. It will begin to expand, almost magically, but of course, tiny air bubbles are being caught in the thick liquid, creating a substance sort of like shaving foam at first. You can keep adding water, but keep the mixer going, and mix at the bottom and top of the pail, to ensure it's mixing nicely. Mixing at the top also brings more air into the mixture, and it will continue to expand, the more you mix.
I stopped early to take the last photo, but it made a full pail after I continued mixing. Just be patient as it could take up to five minutes. If nothing is happening, try adding a bit more water and it should continue to expand. Don't make the mistake of adding too much water too soon. The initial thick blend must slowly mix with water and make air bubbles, and too much water will dilute it and it won't work properly. Just let it expand and add a bit more water if you need to.
When you're done, rinse off the paint-mixer, wash the blender and now you have a very large bucket of a very nice substance. It's a cross between shaving foam and marshmallow goo, depending on how much water you mixed it with, and how much of the dry ingredients you used.
Once you buy all the ingredients, they will last a very long while and you can make a large amount of this stuff without spending a fortune.
The photos show the ingredients and how you go about making it. Very easy.
wam_guevara said: I see they have Sticky and saucy Yuck.. did you try both?
The 'saucy' yuck is similar to the powder found in absorbent products, such as diapers and sanitary pads. It's sort of like applesauce, but not as slimy. I don't really like it, as the slimy and sticky factors are important to me, the way marshmallow goo and corn syrup are sticky and slimy. I bought a bag of saucy yuck, and wound up putting it into potting soil, as it stores water when the weather is dry, then absorbs it again when it rains.