I made my volcano out of an upside down flower pot, plaster of paris bandages and paint. I too was wary of the reactions of ammonium dichromate. I have tried baking soda vinegar couple times too and it does come out pretty cool. The last few years I have added liquid ivory soap which you can find in any grocery store. Make sure you get the white stuff rather than the clear as the lava will come out better that way.