Post #197608 by Palama Tiki on Fri, Nov 11, 2005 1:27 PM

here's a couple more ways to do this.

one is to do the 2x4/chicken wire/diamond metal lath support structure as previously mentioned in other posts, then use hypertufa as the 'concrete'.

hypertufa is a mix of portland cement (not pre-mixed concrete), sand and peat moss. the mix ratio varies depending on what you want to do. this is lighter weight than regular concrete, but very durable. also, as it starts setting up, you can use a wire brush and dislodge the peat moss from the mix, leaving voids similar to volcanic rock. once dry, you can paint to suit.

I used this method for a volcanic flow feature in some landscaping. if you ever made mudpies as a kid, you can do this.

here are some good links and mix ratios:

http://blkrose.8m.com/yard/hyperlinks.html

http://www.whatcom.wsu.edu/ag/homehort/hypertufa.htm

http://www.webspace4me.net/~mikehill/pages.aux/pond/hypertufa/hypertufa.html

http://www.webspace4me.net/~mikehill/pages.aux/pond/construction.html#mason

read thru these, then get some material and try it out. it's one of those things where you just have to do it. use wire brushes, trowels, etc to get the effects that you want.

take a look at these lava flow photos to get an idea of how, well.... lava flows.

http://www.arnottslodge.com/hvn.html

Another way to get a rock-like effect with lightweight and low-cost materials is what Halloween prop-designers call "Monster Mud"; a 5 to 1 ratio of joint compound and paint over burlap. Again, you build your support structure, then cut large pieces of burlap (purchase at a Home Depot or Walmart) to fit the structure, mix 1 part base paint (whatever base color you want your rockwork to be) to 5 parts joint compound, then dip the burlap in the Monster Mud mix. apply the burlap to the wire mesh (attach with small wire ties to hold in place), then slap on more Monster Mud until you achieve the desired effect. (wear rubber gloves and be careful of sharp points on the chicken wire, or especially diamond metal lath). once dry, you can paint. the nice thing about using burlap is that you can crease it and fold it however you want to make fault lines or flow lines, etc.

here's a link for the details of MM and the mix:
http://terrorsyndicate.com/Terror_Syndicate_Monster_Mud_History.html

I used this method to make two 4-foot tall snow-covered 'mountains' for a Christmas display. For those, i built a 2x4 perimeter base, drilled into the 2x4's and attached rebar, and bent it to the general shape of the mountains, then covered it with chicken wire, then coated in burlap and Monster mud, painted and urethaned. they came out pretty good.