Making Silicone Moulds and Casting in Resin

Introduction

When I was building my 1/48 Mig-29A I used one of the front wheel door parts as a mask while I sprayed the camo.  I (wrongly) assumed that there was a replacement in the Aires wheel well set I installed and to make the part fit I altered it.  This made it useless for its intended purpose.  I did have a the Eduard 1/48 Mig-29UB which has the same part so I could have used that, but that would render that kit useless.  So, I decided to cast a replacement part from resin.  As I was going to do this I thought it might be a good idea to make this tutorial to show how easy it is to do.

Making the Mould

What you need

In order to make the mould you're going to need the following materials: Silicone Rubber, Catalyst, a clean mixing cup and a flat sided spatula (I used the handle of a disposable knife).

You're also going to need some latex or nitrile gloves to keep this stuff off your hands as it is really sticky and according to the directions it can be hazardous.  I have shares in this company so I recommend the brand :-)

Preparing the Master

The part in question (the master) was given a cleanup and was temporarily cemented to some plasticard.  This was then glues to a resin block with super glue.  There is a small hole in one end and since this would create problems getting it out of the mould it was filled with a small amount of PVA.

A suitable container for the mould was found.  In this case it happens to be a blister pack from a resin update set.  The master was stuck to the bottom of this using some plasticine.  You can also see that I have taken the opportunity to cast another part at the same time.

Pouring the Mould

I measured the length, width and depth of the container that I was using as the mould.  It was 6cm x 3.8cm x 2cm.  This give a volume of near enough to 40ml.  You can convert this to a weight of required silicone but since this is close to 1g per cubic centimeter I chose to work with the volume instead.

I measured out 40ml of water and poured it into my mixing cup. Using a permanent marker I marked where the water came up to.

The water was then discarded and the mixing cup dried thoroughly.

The silicone rubber was then poured into the mixing cup up to the mark.  You can see I overshot a little as this stuff is really thick to pour.

For the amount of silicone rubber I was mixing I added 1.2ml of catalyst to the raw silicone.  I then mixed it with the handle of the knife.  You should try not to get air into the mix but it is really difficult not to.  Professionals would put the mixture into a vacuum chamber to de-gas the silicone after it's mixed but I don't have that luxury.  Also make sure that you scrape the sides and bottom of the pot while you're mixing it.

Once it was thoroughly mixed the rubber was then poured slowly into the mould.  Start from one corner and let the rubber flow slowly around the master.  This will minimise any chance of getting air bubbles.   Again, professionals would do a second de-gassing at this stage and again I didn't.  Once it is full set it aside for 24 hours to cure.

After it has cured you can remove the hardened silicone rubber from the container...

...and then remove the masters.

Casting in Resin

What you will Need

To do this part you will need.  Part A and Part B resin, latex or nitrile gloves, a container to mix in, something to mix with and either two measuring beakers or, as I am using, disposable pipettes with measurements on the side...and of course your silicone rubber mould.

Put on the disposable gloves and measure out equal quantities by volume of part A and Part B resin.  Add these to the mixing cup and stir thoroughly.

Once mixed pour the resin into the mould.  In my case I used a third pipette to transfer the resin to the mould.  Experiment with what works best for you.  The trick is to get the resin into all parts of the mould without getting any air bubbles.

As the resin sets it will turn white.  Leave it for 20-30 minutes before removing it from the mould.

Success.  Perfect copies of the originals.

Be prepared for some failures though.

I hope that you have found this useful.

Hobby Boss 1/48 Ta-152 C-0 - Part 2

Back to part 1.

Somewhere to Sit

Like most model aircraft, construction starts with the cockpit.  Since I'm using the Eduard detail set some of the plastic bits won't be used.  I started by removing the bits that were going to be used from the sprue.  These were test fitted into the fuselage before gluing selected pieces.

The cockpit sidewalls are photoetch.  These have a lip on them at the bottom which required careful folding.  I don't know how I would have done this if I did not have the right tool for the job.

The rudder bar and the control column have been offset a bit.  Since the kit has poseable control surfaces I'll place the ailerons and rudder to match.  I'll have to remember to pose the tail wheel too or it might look a bit odd.  Detail as been removed from the side consoles.  This will be replaced with photoetch once the cockpit has been painted.

The photoetch rudder pedals from the kit were added to the rudder bar.  I was going to use the Eduard replacements for this but one of them flew off into space as I cut it from the frame.  I should have known better than to cut it unsecured.  Of course after hunting around for it on the floor for about 20 minutes and then deciding to use the kit rudder pedals, I found it right next to the sprue it was cut from after I had done all the painting.

Looking at the layout of the cockpit it is apparent that Luftwaffe pilots had unfeasibly long legs in order to reach the rudder pedals.

The cockpit was given a coat of paint.  Luftwaffe cockpits of this era were painted in RLM 66 Black-Grey.  The closest colour I have to this is Vallejo 71.055.  The cockpit was drybrushed in a lighter shade of grey and then in lightly Citadel Chainmail.  Scratches were done with a prismacolor silver pencil.  I also sprayed the engine bay and the area around the tail wheel.  These were in Vallejo  71.044 which is a good match to RLM 02 grey.

The cockpit was given a gloss coat and a few placards were placed using the Airscale WW2 Luftwaffe Placards set.

Another gloss coat and then the Eduard photoetch side panels were applied and the whole thing was given a wash with Lamp Black oil paint and Raw Umber for the leather on the seat.  Applying the oil wash over the photoetched parts helps blend the colour in.  The Eduard photoetch has a distinct blueish hue and the oils know that back a bit.

Assembling the instrument panel was fiddly.  One of the tiny parts did fling off into space when I picked it up in the tweezers.  It's hardly noticeable though...unless you notice it that is.

I also assembled the lap belts for the seat.  I have not folded them onto the seat at this stage so the seat looks like its trying to grab a victim in some b-grade horror movie.  "Leeetle 1/48 scale pilot you must sssit on me so I can eeeat you!"

The cockpit parts were given a coat of matt varnish and Crystal Clear was put into the instrument dials to simulate the glass.  Finally the tub was installed into the fuselage.

Next time I'll work of the engine and the tail wheel and hopefully get the fuselage sides together.

On to part 3

Academy 1/48 Mig-29A - Part 12

Back to part 11

Rise Up

Alrighty then.  Time to get this baby onto it legs.

The landing gear and the inside of the gear doors were all given a coat of Tamiya XF-66.  Details on the legs were picked out with citadel boltgun.  The wheels themselves are Gunze H77 and Tamiya X-05 Green.  The red mark on the tyre and rim is the tyre slip indicator.

At last I can get the gear in into the aircraft.  They're only a push fit at the moment but it's really starting to look the part.

Finally the gear was cemented into the wheel bays.  However I do have a confession to make.  The strut in front of the nose gear is pinched from the Eduard Mig-29UB because I wrecked the one that came with this kit.  I used is as a mask for the front wheel well and to make it fit it required...well...surgery.  I'll have to get a replacement made as the part in the photo below is only there to make sure the nose gear is placed correctly.

Once the gear was fit I attached the gear doors.  These were very fiddly and some of the small resin parts broke requiring me to fix them as I worked.

Time in the Office

I also worked on the ejection seat and finally got it glued into the cockpit.  The Aires photoetched harness was tricky to work with but they came out alright in the end.

The office now looks busy - like the real thing.

I used some white Vallejo pigment inside the engines to replicate the white dusty soot often seen inside the business end of fighter jet engines.

Next time I'll finish the weapons and assemble the airbrakes.  Then there's just final detailing and we're done.