SRMW Threadwell Textile on the S&S RR

[S&S RR]

This is great stuff, John - thanks a bunch for taking the effort to post!

Vince


Thanks for following along - I just setup a hot spot with my phone and will continue without the cable internet. At least until I use up my 8 Gig of data.  Cable company are you listening.

[S&S RR]

So here is a picture of the mold boxes after the sides are glued on.  I have arranged the castings to minimize the amount of mold material for the larger castings. Once I have everything in the mold box I spray it "lightly"  with the Mann 200 mold release. I do mean  "lightly", I just give it a slight dusting.  I have been using this same can of spray for years.

[S&S RR]

The next step is to make full use of the mold and add some smaller parts in the holes. I have the FSM G. Wilikers kit 4th in line on my build list, so I opened up the castings box and found a few castings that I wanted to duplicate for my scratch build parts drawer. I have already gone though this process with Fox Run and Sewall's which 2 and 3 on my build list.

[S&S RR]

We are now ready for the silicone rubber mold material.  My "go to" material is the 10:1 material sold by MicroMart. The molds are Pink.  I have made hundreds of molds with this stuff and it's great.  The downside is that it is expensive. I made most of the molds for my rock castings using this material. For this set of  molds I'm trying a new material "suggested by Tom here on the forum". It is a little less expensive and I can order it on Amazon prime so I don't have to have a large order to get out of the high postage cost.

[fsmcollector67]

John,
Maybe I missed it, but how do you affix the pieces to the mold so that they do not float up in the mold?

Loren...

[S&S RR]

John,
Maybe I missed it, but how do you affix the pieces to the mold so that they do not float up in the mold?

Loren...

Loren


Great question, but I have never attached them to the box. The weight of the metal castings or plaster castings holds them in place in the box.  If you were duplicating something that was very light I would glue it down to the mold box. I have good luck pouring directly on the castings and have never had any problem with them shifting around.  Gluing them down would not hurt anything but may make it more difficult to get them out of the mold and mold box without breaking them after the pour.

[S&S RR]

I did forget one important step. Before you pour - inspect the mold box and castings for the little strings of hot glue. Unless you want some out of scale spider webs. I do this at least three times with different light sources. It is time well spent because if you miss one you will be making another mold. You can pick them off with your fingers or tweezers. 

[rpdylan]

John,
    is this the "Oomoo 30" product on Amazon that you are using for the mold making?

[S&S RR]

John,
    is this the "Oomoo 30" product on Amazon that you are using for the mold making?

No - I have tried Oommo 30 and it is too soft.  Even the simplest of details pull off in the mold with resin.  I'm using Star 30 which is made by the same company.  I will post pictures of the bottles.  Please stay tuned.

[S&S RR]

Here is the box for the mold material on the left and my preferred resign material on the right. It is important that you get the Star 30 mold material and the 305 resign material.  I have had unsuccessful experiments with the cheaper materials made by the same company.

[S&S RR]

Here are the containers with the Part A and Part B. Smooth-On makes a number of different mold materials and resins - this is the Star 30 product.  Please note: I corrected this post it originally said Star 35 product. Typo

[S&S RR]

I use clear plastic disposable cups to mix the silicone rubber - with this material you mix 50 % A and 50% B by volume so the cups work great.

[S&S RR]

I simple gun site the cups to make sure I have the same amount of each component. I then pour the contents of these cups into a third cup and mix them together with a popsicle stick. I don't have a picture of the mixing process because once you put the two components together you need to stir. It needs to be a gentle stirring motion that does not introduce air into the mixture.  If you see any white streaks as you dig along the sides of the cup you need to keep stirring.

[S&S RR]

Once I'm sure the components are mixed completely I pour the liquid into the mold box. I keep pouring until I have the castings covered (in this case at least 1/16 of an inch on top of the highest point in the casting. Since this was my first time using this material I was a little uneasy about being able to see the castings - the 10:1 material is opaque enough that you don't see the castings once you have them covered. I tested the depth to the high point of the casting with a toothpick just to be sure.

[S&S RR]

I then use my home made shaker table - a rubber mallet - and make sure that any bubbles shake loose and rise to the surface.  I only saw two bubbles with this pour.  Usually I break loose more.  I'm simply hitting the sides of the mold boxes to create a vibration. In commercial casting operations they actually have a shaking table that does the same thing.