Casting with Clear Resin?

Hello all.

I am giving casting a try and using Clear Polyester Casting Resin made by "Castin' Craft" and not getting very good results.
My molds are made of RTV Silicon and freshly molded.
Yet the finished product from the mold is substandard.

Is there a better resin I should be trying or am I doing something wrong with the Castin' Craft resin?
Any hints would be helpful.
Oh, and yes I am new to the resin casting world.

Thanks, Barry.

 

Some silicones exude alcohol after curing, you might want to try warming up your molds before mixing-up and pouring your clear resin into the mold.
(Also make sure that you thoroughly mix the material)

Years ago when I worked at Icons we did some tests for the Batman and Robin Batarang bases, one of which was Clear like Ice, we pre-heated the molds and that did the trick so we didn't have a tacky surface.

 

Castin' Craft resin is one of the worst products on the market.

Smooth On makes some great resins and in fact, I'm using Crystal Clear 220 right now. No, really. I have a batch in the pressure pot as I'm typing this.

 

Ya but Crystal Clear 220 says not for home use, only for industrial use and to use Smooth-On mold max silicone.
Also to heat mold prior to pouring casting material.
Sounds good but many hoops to jump through to get it to work.
That would mean ordering a whole new kit for casting and mold making.

 

I use it at home.

I don't use their silicone either.

 

You are pressure cooking right?

 

Do you mean me? You have to use a pressure pot with Smooth On or you'll get bubbles.

As far as I know, any quality resin will require pressure casting. Floral resins and Castin' Craft can cure without a pressure pot but the finished result is often times less than desirable.

 

Do you have a picture of a pressure pot, cause when ever I cast I usually use this thing at my dads work, you put the mold on top and then it starts to vibrate....Its hard for me to describe it.
-But I think he may have a pressure pot at his work too, I just wanna see if it is or not.
-Thanks.....

 

Let me tell you exactly what I am doing.
All I want to do is cast a clear canopy and thrust nozzles from my Revell/Monogram Viper. The molds I made look pretty crude but work fine but the end product is less then desirable. This is not for any kind of production run, just a one off for myself. I always wanted the MMI seated figure and Cockpit Detail Set but just canÂ’t wait any longer. I decided to try making my own by getting a Starter Resin Casting Kit from MicroMark. I thought that would give me a good starting point to get my feet wet with the whole resin casting seen. When I got this kit and the CastinÂ’ Craft stuff, I didnÂ’t know about this board or I would have been asking questions first.

I know of some superior products now, thanks to all you fine people, but canÂ’t justify spending more money on quality resins and a pressure pot to go along with it. How much would the pressure pot cost or could I make my own home made one out of everyday supplies.

 

Well, with my first few casts complete, I can honestly say that the Castin' Craft resin is garbage. I am sure it is fine for other things, but definitely not for RTV molds. The first canopy was sticky with very fine air bubbles trapped in it. The second canopy was poured and put into a closed box with a halogen lamp for 6 hours to create basically a light bulb oven. The canopy wasn't sticky this time but was cloudy in certain areas and not smooth as I was hoping.

I tried to salvage the first casting by dipping it in Future Floor wax a couple of times to smooth things out and hopefully make it a bit clearer. From a distance it is passable but up close is a different story. I will probably use the first cast but cannot use the thrust nozzle cast because it shrunk considerably. Boo hoo for me, I will need to find a better Clear resin that doesnÂ’t require a pressure pot.

Now the question is:
What clear resin can I use that will not shrink or shrink very little and not require a pressure pot?
:confused

 

Getting all the air bubbles out without a pressure pot or vac pot to assist you is going to be very hard, as for shrinkage I doubt you will notice it in a better quality resin... If you don't want to pony up the money for the Smooth On stuff then check out http://www.alumilite.com/dealers.cfm and find a store near you that carries it, call first to see if they have the clear stuff most of the stores by me carry a little selection but only one carried the clear... It works much better then the Castin Crap but because it kicks pretty quick trapping the airbubble that are going to haunt you just like most clear resins...

That would be a vibration pot/table, it certainly helps drive the bubbles to the top (same as a vac tank), but a pressure pot squishes any left over bubble down to a very small size that you generally can't notice...

 

www.harborfreight.com has a sale on now. Pressure pots are normally $80 from there but it's now $40. I have this price from a printed catalog. It's probably the same online.

 

THANKS
The resin I'm gonna use is from smooth on, and it says it has minimal bubbles, so if I use the vibration pot/table, would that would the cast down to almost un-noticable bubbles?

-Thanks.

 

In theory yes it will help as long as you don't create too many bubble while mixing and pouring... But, remember it's a give and take you have to mix it well but you only have so much time before the mix kicks and traps the bubbles... If you mix fast you will create more bubbles but you will have more time before it kicks to get them out, and your pouring technique can remove or create bubbles as well...

Mostly it's going to be a trial and error, taking notes (room temp, mold temp, humidity, elapsed time) and finding what works best for you...

Although I have yet to try it I hear that Platinum cured silicones are much better for clear castings, although I have not tried them yet... But, I have experienced color bleed from the Tin cured silicones I have used, creating a slight tint to the first 2-3 pulls...

 

I went to their website but found nothing that looked like a "pressure pot".
I used “pressure pot” in the search engine there.
Are you sure that's what it was described as?

 

You have email.

 

For the pressure pot are you talkinga bout the 2.5 gallon paint pot?

Jedi Dade

 

What is the thickness of the Crystal Clear 220?
Is thick like maple syrup or does it have more of a consistency of milk?
I would hope that it is more like milk for ease of pouring into to the molds.

WouldnÂ’t a vacuum canister work better then a pressure pot for removing the air bubbles?
How hard would it be to create such a device?

 

Pressure Pot/Paint Pot, same thing. You definitely need to use pressure when dealing with clear resins.

Polyester- almost useless in most tin-cured silicones. Polyester relies on heat alone for its cure and will start to cure from the thickest point in the part and the cure then works its way outward to the surface of the part. This means the center of a part will become solid before the surface against the mold. Because polyester has a high rate of shrinkage, the center also shrinks and causes the surface to 'squirm' against the mold, often creating wrinkles or cracks. Heating the mold does help, but if too much heat is used, the mold will swell and become useless (it doesn't 'unswell'). Platinum cured silicones will produce a better polyester part.

Clear Urethanes- most have very long cure times, which helps in that you can wait for some of the bubbles to come to the surface. Only the smallest will remain and either vacuum or pressure can be used to get rid of them. Pressure is better as none of the chemistry will cook-off in the low pressure environment associated with vacuuming. It should be noted that bubbles are not 'shrunk' during the pressure process-- they are forced into solution with the resin.

One thing not addressed in other posts is the quality of the final part. You can get the best casting material made and have it work perfectly, but unless the master is constructed with the intention of creating a 'clear' part, items such as canopies will not be as optically clear as one would hope. The only way to know if a master will produce an optically clear part is if the master is polished such that surface flaws are not observable. In other words, if the master is not clean and shiny like a mirror in the places where the part is supposed to be clear as glass, the 'clearness' of the casting will less than satisfactory.

Given the cost of producing an unsatisfactory part, if this project is really for only one part, you'd probably be better off just scratchbuilding it. Unless you do have a very clean and shiny master.

Scott

 

Crystal-clear 220 is not quite as thick as maple syrup but in does flow well. Here's a picture of a prop I made using Crystal Clear 220:

[image]http://www.jedi-academy.com/personal/14.jpg[/image]

The resin had to flow around each part as it was held in place above the mold.

 

Thanks guys,
IÂ’ve gotten one decent pull from the mold, and with a little clean up, it should be usable.
IÂ’ve dipped it in Future Wax to smooth it up a bit and it seems to have done just that.
Its still not as nice as I would like but with a little clean up and paint it should be just fine for me.
I think I will use the canopy mold to create a totally solid piece and let it cure and then remove all the frame structure.
I would then polish it to a mirror like finish and recreate the frame structure and add simulated rivets and then use it as a master and create a vacuum form canopy.
I have tried vacuum forming before and have had success with it.

Again, thanks for all the help.

 

I searched for "pressure pot" and found 2-1/2 GALLON PRESSURE PAINT TANK by Central Pnuematic. Is this what you mean?



http://www.harborfreight.com/cpi/ctaf/Disp...temnumber=37515

Holy Schnikeys, the price is $79.99

and Pressure Paint Tank.

 

Yes, that's the one I use. I originally bought one from www.alumilite.com but I had trouble with the handles so I upgraded to this one.

 

Alright, so do you pour your casting resin into your molds then place the whole shebang into this thing and turn it on? Does it hook up to a compressor? Shouldn't it suck air rather than blow? Please explain the process in detail.

 

The inside of the pot is concave, so I made a tray to fit inside the pressure pot out of MDF. I bought some metal U's from Home Depot to use as handles. This gives me a flat surface instead of a rounded one and keeps the mold level.

You have to hook a pressure pot up to a compressor. When you use compressed air, you're basically squeezing the air bubbles to a size you cannot see with the naked eye.

You can use a vacuum chamber instead and some people prefer vacuum to pressure for clear resin but I've had good results with pressure so I see no need (for me) to buy more equipment.

 

MDF?

Vacuum 'chamber'?

 

Medium Density Fiberboard. You can find it at Home Depot in the same section as plywood. It is commonly used for inexpensive furniture.

A vacuum chamber is similar to a pressure pot. Some are as simple as a large strong tube with thick plexiglass on both ends. The suction keeps the lid in place. I really can't comment TOO much on them since I've never used one.

 

I found out yesterday that my dad has a pressure pot at his work so I cast an inch by and inch block of ortho resin and its hard as rock so I'm gonna carve that down into my anakin ears, the bubbles are soo small too, this pressure pot worked great.

 

Try clear urethane. There is a few companys who make it. Doesn't shrink like resin and doen't need mold release. Comes in clear and can be tinted. I have the number at work I'll try to get you that info. They send out samples out free and a very cool DVD on how to make molds and stuff. Very informative. Old hat for me but for the novice it perfect.

rick