Saturday, 3 March 2007

Resin Casting Tutorial: Part V (and last)

(versión en Español)


Now that we have the mold ready, we can start casting some pieces.

We'll need: Quick setting utrethane resin, plastic cups, wooden toothpicks, a tool for removing the mix, latex gloves and some polyethylene shopping bags for protecting the table below.

I cover the vibrating tray with polyethylene. The great thing about this plastic is that you can scrape the resin from it once is cured.

You can never get enough protection. This will protect you eyes or glasses in the not so very unlikely event that a resin drop gets close to your eyes.

I start measuring the same volume for components A and B. There is not an exact method to know beforehand how many resin will you use in a mold (never, NEVER, try to measure it with water. A single drop of water will ruin some some kilogrames of urethane resin by itself). So just try to get used at wasting some resin each time you make a mold...

Once the components get in contact the clock is running! You have about 120 seconds before the resin gets too viscous, more than enough. Time will vary depending on the room's temperature. Resin will set quicker at higer temps.

I normaly mix the resin during 20 seconds and then pour it, you should experiment what settings suit you better, but remember that the resing must be completely mixed for better results.

I switch on the vibration tray, put both mold's halves on it and start carefully pouring the resin.

I pour some resin on the other half to avoid bubbles when closing the mold.

Now I pick a toohpick and remove any remaining bubbles. You should be vearing eye protection when doing this. Those bubbles are very small, so you would be forcing your sight, closing to the mold while you are messing with the toothpick so an accident could happen in no time. Remember: "safety first".

The resin is starting to set. you will notice that larger volumes set faster than smaller ones.

When the resin is gooey, I close the mold in a quick motion and gently press the excess resin out. Some call it the "sandwich technique".

You should remember that your urethane resin is very sensible to humidity. It's better to recap the bottles during all those operations.

I am casting another piece here. I made a mistake in the last one. As I did not cover completely the second half with resin, I got some empty spaces to fill with putty later on.

This time I prepared too less resin... Well, this is not a problem.

I just prepare more resin, add it to the molds and repeat the "Sandwich Technique". You'll notice that gentle slope we were talking about when making the mold. Its function is to accomodate a little excess resin wich will be expelled out when pressing the "sandwich".

Here is the completed piece. Nearly perfect! Altough there are some minor bubbles that I'll fill with putty in no time.

And that's it! Hope you find this tutorial useful.

Next time, we'll talk about scratchbuilding techniques. We'll follow a step-by-step process to do a T34-like turret for Warhammer 40K games.


Luke said...

Great tutorial! Really well explained and comprehensive - looking forward to trying out some casting.

the95th said...

Assuming you are careful, how many uses can you get out of one of these molds?

Anonymous said...

GREAT!thank you.

Anonymous said...


mastershaper said...

Very useful tutorial Ultrawerke!
I would like to ask you, which kind of resin you utilize? In Italy I can find a polyurethane resin from a company called Prochima but the quality is poor and the pieces I have cast has lost volume in time (2/3 weeks after the cast). Can you suggest me a modelling company with a good resin to buy? Thanks! Andrea

Anonymous said...

I second "mastershaper's" request for a good resin company. i see that you use Feroca, but i do not know what type you use. i do not speak spanish and find this very frustrating to try and figure out. please shoot me an email at ""

thanks a ton!

GDMNW said...

Great tutorial. I haven't seen the sandwich method before!

I especially appreciate your taking time to point out how to deal with problems like water in the mold or not mixing enough resin.

Not to mention that the tank you have made is amazing too.

Anonymous said...


That is really interesting stuff, ! Thank you.

I was wondering, about the other methods, specifically the "suspending method".
I know it might trap bubbles easily, but :
Imagine you do the same steps but instead of putting it on some clay, you suspend the model for the first part of the mould.
Once the two-parts mold is finished, you do again one step to recreate the first mold part (because it likely had air bubbles trapped under the model).

What I mean is, that would help having a real good mold with a really good flat seam without a first half full of bubbles.
Because in your case the base is really flat so clay is ok, but thinking of a more complex shape it might come in handy.
It might sound a bit more expensive, but, you can always use pieces of the old first part in its second version as you say.

What do you think ?

Cheers for the tutorial,

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