40K 25mm Bases: First cast

The mold for my 25mm bases came out better than expected.  When glueing in the masters, I took extra time to make sure to make sure the seal was even and without any glue build up.  I was rewarded with cleanly cut cavities for each base.

 finished mold

Finished Mold

 25mm bases 500pxl

Finished Bases

mold with tool thumb

After removing the Lego mold box, I got out my handy sculpting tool.  Some times the mold is difficult to release from the master & a bit of soft scraping is needed to get under the mold.  But in this case, all that was needed was a bit of finger pressure to release the mold.

mold and master

The 10 master bases survived the molding process & are still firmly attached to the MDF base board.  If need be, I could remove the bases & use them on figures.  Instead, I’ll store the bases right on the board in-case I need to create a new mold.


Not the best of pics, but you can see a bit of a lip running along the edge of the mold.  Every new mold needs a bit of clean up where the RTV rides up the side of the mold box.  The build up will cause the mold to sit at a funny angle when casting, take a razor and remove the extra RTV. 

 rivet holes

A bit of an oddity on the cast bases.  If you look closely at the masters, these two bases have a total of four rivet holes drilled into them.  But the cast bases have all manor of results at the drill holes.  The beam on the left has an outie rivet.  The decking to the right has everything from a small cavity to a counter sunk rivet to a full fledged outie.  All of these are caused by air bubbles getting trapped in the drill holes when the RTV was cast.  One of these days, I’ll remember to pick out holes such as these with a tooth pick while pouring the RTV.  Until then, I’ll continue to be interested in the what effects an unintended gas bubble can have.

  1. #1 by Trevor on September 2, 2009 - 1:14 pm

    Could you detail what materials you used for creating the mold and then the castings?

  2. #2 by chicagoterrainfactory on September 2, 2009 - 2:18 pm

    Both the Resin and RTV are from Smooth-On.com

    The resin is the Smooth Cast 300 with the 3 minute pot life. The RTV is Mold Max 20. The 20 refers to the softness of the rubber – Mold Max 30 would be a stiffer RTV. Use 20 for masters with undercuts, use 30 for flatter objects which need long, smooth mold walls.

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