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Clinic - Making Your Own Rock Molds

     The first step is to find a rock with suitable strata.  (Strata - the lines or detail of the rock.)  The idea is to find a rock where the details aren't too big for your scale.  For HO scale a lump of coal makes some of the best molds.  I also created some of my best molds from layers of compacted dirt.  The detail there was amazing.  It really helps to have rocks from the area where you are modeling.  If you are making a mold from a piece of limestone it will not look like granite when you make a mold.  Research the area you are modeling to find out what kinds of rocks are common in the area.  If possible, go to the area and find samples.  The more you have seen the area and the more color pictures you have the better your created rocks will look.  I model southwestern Colorado.  The types of rock there changes by elevation.  With that in mind the strata will change the higher I model and the color will change as well.

     Once a suitable original has been located you will paint several layers of latex rubber onto to to create the mold.  This rubber will not stain or harm the original in any way.  Woodland Scenics and several others have the latex rubber product that you can get from your hobby shop.  If you are using a rock or something besides compacted dirt, wash the original to remove any loose dirt.  Using a CHEAP paint brush (the 12 for a dollar stuff you give your kids) paint on a coat of the rubber to the original.  Allow this to dry completely.  Once the first coat has dried paint on a second and, again, allow it to dry completely.

     For the third coat you will want something to reinforce the mold.  Some people use gauze from a first aid kit.  I like using my wife's runnered panty hose.  She was going to throw them out anyway...waste not...want not.  If you don't have any on hand it's cheaper to buy the gauze.   Paint on a coat of rubber and then press the hose or gauze into the rubber.  Then cover with more rubber on top of the reinforcement material.  This will create one think coat that completely encloses the reinforcement material.  This will keep the mold from tearing as you flex it around.

     Once the third coat has dried completely you are ready to remove the mold from the original.  Wash any dirt from the mold and you are ready to make mountains.  Do not use cast resins in molds made this way.  The heat created by the resin's curing process tends to cook the mold.  This I have learned the hard way.  I have several of these molds that I created in the late 1980's that are still just as good as they were when I first made them.  Store the molds in a cool and preferable dark location when not being used.  

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