Water clear, bubble free resin casting...

[SurferGeek]

I know that there have been several threads over the past months regarding clear casting but many of the posters' "requirements" for their final products were varied.

I'm probably setting myself up for failure here because I've not tried my hand at resin casting at all and to start with clear casting... I'm a very meticulous person and I plan on taking everything slowly and methodically so I hope to be able to pull it off.





I have a 1 inch by 4 inch part that will need to be water clear and bubble free, as well the finished piece needs to be HARD, not brittle but hard enough to not dent or deform. The piece is very simple with little detail or complex shapes so claying it up shouldn't be too hard. I don't mind putting extra work into making the mold(s) but when it comes to casting I want to be able to do this in a minimum amount of steps.

Questions:

1. Cost aside, within reason of course, what is the best resin? Most posts I've read lean towards Smooth-On.
2. Will I be required to use a pressure pot?
3. What is the best release to use? I remember reading someone mentioning "Tire shine" as a release... Is this a brand or are we talking Armor All? I would like to demold these and have minimal finishing work. I want the smoothest, shiniest, glass like casting possible.
4. I understand to use silicone free clay for the mold but is there a preferred brand?

Thanks for any/all comments and opinions.

 

[TK648]

Check the smooth-on site for their FAQ page
and give smooth-on a call their tech support is very good

Good luck with your project


Andrew

 

[Hadleys Hope]

You can buy the clear casting resin they sell at Michaels and place your mold in a pressure pot and voila you have crystal clear castings. Good luck.


Paul

 

[LeMarchand]

if you are going to pressurecast the resin, make sure your silicone used for the mold has been degassed in a vacchamber. When you don't this and you cast under pressure you will get goosebumps all over your part. I also heard that you can pressurise your silicone mold when it is curing.

Marc

 

[Mxlplx]

All above info is good. I suggest smooth-on also. If you don't go the vac pot route, and are lazy like me, I find that trying to get a bubble free pour is possible, but tough. You can start by getting a resin that gives you time to pour slow. Start by pouring from one corner of the mold, and do it very slowly in a thin stream. This will not ensure a bubble free product, but helps. Otherwise, do it right and vac it for the best results.

 

[Blad]

<div class='quotetop'>QUOTE(SurferGeek @ Apr 25 2006, 05:01 AM) [snapback]1232599[/snapback]</div>

4. I understand to use silicone free clay for the mold but is there a preferred brand?

Do you mean a clay mould? Or a clay master?

To get the shiniest finish on your casts you really need a shiny finish on your master. If you wax coat your clay master and polish it up before casting in RTV you should get a shiny finish.

I won't bother with brands, because UK brands aren't going to be relevant, but on a small piece like this I asume you will be using an open mould? You won't need a pressure pot or anything like that for a small open mould. just make sure you don't stir in a lot of bubbles when mixing and use a toothpick any bubbles that surface. You should have plenty of standing time for any bubbles to rise, but a couple of taps on the side of the mould would help, or if the object is rectangular or square, gently poking the corners with a toothpick would release any trapped bubbles there.

 

[blufive]

<div class='quotetop'>QUOTE(SurferGeek @ Apr 25 2006, 12:01 AM) [snapback]1232599[/snapback]</div>

1. Cost aside, within reason of course, what is the best resin? Most posts I've read lean towards Smooth-On.
2. Will I be required to use a pressure pot?
3. What is the best release to use? I remember reading someone mentioning "Tire shine" as a release... Is this a brand or are we talking Armor All? I would like to demold these and have minimal finishing work. I want the smoothest, shiniest, glass like casting possible.
4. I understand to use silicone free clay for the mold but is there a preferred brand?


[/b]

Don't bother with the clear resin you can buy locally. I've read where some RPF'rs have had decent results but most of them still acknowledge it isn't good, it's just cheap.

I use Smooth On Crystal Clear 220. Alumilite also makes nice clear.

You will have to use a pressure pot and compressor.

I don't use release anymore but I have used Mann's from Smooth On. I now use talc in my molds. I'd be interested in seeing how Tire Shine works but you might have to buff the piece a little when it comes out of the mold.

I think you're thinking of sulpher free clay. Sulpher can cause issues with rubber. I use Kleen Klay from MicroMark.com.

I hope this helps.

 

[SurferGeek]

Thanks for the replys so far... It was late last night so I'll clear up some of the "cloudy" comments.

The piece I'm molding is an original part so it won't have to be modeled, the clay I was referring to would be used to make the two piece mold. I could do a one piece split mold but I've heard mixed results with those... Also, I don't want to damage the surface of the original while splitting open the one piece.

As for vacuum degassing the silicone mold... Can I cure the silicone mold in the pressure pot as well? I don't want to have to buy an additional piece of eqipment and I assume you can't do both pressure and vacuum with the pressure pot. Or do I truely need to buy/build a seperate vacuum chamber?

The surface of the original is relatively glass smooth already, it's not glass but smooth nonetheless. So, having a smooth mold should be a sure thing, I just want to ensure that the resulting casts are as smooth as possible as I don't want to have to sand or polish them if I don't have to.

I've heard and read that local hobby shop clear resins is a crap shoot and the two resins most often discussed are the Alumilite and Smooth On products so I'll likely go with one of the two. I've read that I can get the Smooth On in pints by calling. Looking at the SmoothOn website regarding their clear casting resings... Has anyone used any of the Crystal Clear 200, 202, 204 and 206 products? I realize they have very long curing times but since they aren't heat cured do they have a better chance of being bubble free?

 

[blufive]

You can buy a vacuum pump and really thick acrylic (about 1/2" thick) and make your own vacuum chamber by using the pot from the pressure pot. You would have to buy a vacuum gauge and various fittings to connect the pump to the gauge to the acrylic.

In all honesty, it's way easier to just buy a vacuum chamber from alumilite.com.

I didn't like the Harbor Freight vacuum pump though. You have to maintain 90 PSI to achieve 28-30 inches of mercury for deairing your rubber. I just bought a nice vacuum pump off eBay and while it was a little pricey, I couldn't be happier with the results. It's electric and doesn't tie up a compressor line or make the compressor turn on too often.

I have used other kinds of Smooth On Crystal Clear. The cure times vary but most importantly, the maximum thickness will also dictate which version of resin you should use. All of the Crystal Clear products are pretty darn good.

You don't HAVE to heat cure (or post cure) your clear castings. I called Smooth On about that. The tech guy said it depends on how the part would be used. He was referring to cast pieces being used in industrial settings where they would be put under a great deal of strain by heat or pressure. In those applications, post curing was recommended.

For our purposes, heat curing is not necessary but of course, it doesn't hurt. Just leave the part in the mold during the post curing process.

While I was on the phone with him, I took one of our Cage Communicator castings outside and threw it on our deck a few times. It wasn't post cured and suffered no damage whatsoever.