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#1 dannyi

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Posted 17 April 2011 - 06:31 PM

Hi fellas,....need a little help, been working with clear resin for the past couple days and not having much luck.
...this is what I've tried so far. Working with Alumilite Clear. I have a silicone mold of a spare windshield from the parts box. It's highly recommended from Alumilite to preheat the mold if it's less then a 1/4" thick, so that's what I do. 15 minutes at 150 degrees in a convection oven. I use a gram scale to measure out the resins by weight(also recommended)and mix in a separate container. After pouring the resin in the mold, it's put in a pressure pot, after that it's post cured in the oven for 30 to 40 minutes at 150 degrees. The post cure is recommended to eliminate brittleness. I have varied the pressure pot times from 45 minutes to 6 hours. The first time I pulled the mold from the pot after 45 minutes tiny little bubble started to form around the edges of the mold. Obviously it must not have been completely set up. Even though Alumilite states it has a 45 to 90 minute demold time, every cast after that one was at least 4 hours, up to 6 hours. Here's the last 3 results using the above method......
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....not real sure what I'm doing wrong or what conditions I have that are causing the distortions. Any help would be greatly appreciated!...thanks guys...

#2 biscayne63

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Posted 17 April 2011 - 10:24 PM

Hi,
Check and make sure that your clear resin is compatible with your silicone. Most clear resins will not cure against tin based silicone. Tin based silicone is usually blue. Platinum based silicone is used with clear resins. Platinum silicone is usually clear. If the part doesn't cure and stays sticky until you remove the first surface, this is more than likely a compatiblity problem.

Brian

#3 dannyi

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Posted 18 April 2011 - 04:45 AM

Hi,
Check and make sure that your clear resin is compatible with your silicone. Most clear resins will not cure against tin based silicone. Tin based silicone is usually blue. Platinum based silicone is used with clear resins. Platinum silicone is usually clear. If the part doesn't cure and stays sticky until you remove the first surface, this is more than likely a compatiblity problem.

Brian


....thanks Brian, I really appreciate the info!....that's something I was not aware of. I will definitely look into this.....thanks again!

#4 paul alflen

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Posted 19 April 2011 - 04:42 AM

DANNY, THIS MAY BE A DIFFERENT APPROACH.PLASTIC INJECTION MOLDERS REGRIND PLASTIC.NOW I'M GOING OUT ON A LIMB HERE. WHAT IF YOU REGROUND A FEW OLD CLEAR WINDSHIELDS INTO SMALL BITS. THEN PUT THAT INTO YOUR SILICONE MOLD. THEN HEAT THE MOLD IN AN OVEN, ON A COOKIE SHEET.THE HEAT SHOULD SMOOTH THAT REGROUND PLASTIC TO FIT THE MOLD. THEN YOU SHOULD HAVE PERFECT WINDSHEILD. THIS PROCESS IS SIMILAR TO THOSE STAINED GLASS, CRAFT FLAT- ORNAMENT THINGS . THE STAINED GLASS GAVE YOU A FRAME, COLORED STYRENE PELLETS,AND CLEAR ONES. THE PROCESS IS TO PUT THE STAINED GLASS FRAME ON A COOKIE SHEET ,THEN ADD THE STYRENE,THEN HEAT IT TILL IT MELTS FLAT THEN COOL IT. TRY SOME CLEAR STYRENE OUT OF A STAINED GLASS PACKAGE, FROM THE CRAFT SECTION AT HOBBY LOBBY TO TEST THIS THEORY. GOOD LUCK PAUL

Edited by paul alflen, 19 April 2011 - 04:50 AM.


#5 Greg Wann

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Posted 27 September 2011 - 04:59 PM

Hi Danny,
Are you still trying the clear? Try mixing it 1to 1 by volume instead of by weight. I do resin casting. I made the parts that John Teresi has been building. I have been getting better at using the clear resin. I recently discovered that the clear resin I bought from Alumilite and Aeromarine products are the same brand. Alumilite says to mix it by weight and Aeromarine says to mix it by volume. I am a bit confused by this mixed information. I have better luck mixing it by volume. I pour out of smaller containers that are lab grade bottles. Make certain it is mixed very well. Make a good two part mold. Pressure cast it and do not open for at least three days. Making the bubble tops for the Cosma Ray that John built is easy to do now that I have learned not to touch it for awhile. I have a forum that I post a lot of my resin work on. Email me if you still need help.

Greg

#6 Greg Wann

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Posted 27 September 2011 - 06:05 PM

I was heating the mold until Jeff of Time Machine Resin had me call him to give me some help. The resin heats up on it's own. The only reason that the manufacturer wants you to do this is to burn up your mold faster and buy more silicone. Polishing your master is a must too. The best polish I have found is no longer made. Bare Metal Foil Plastic polish was made for clear parts and works extremely well. I bought up all I could find! It works great on paint too! I talked to the Inventor of BMF a few years ago when I called about the product being no longer offered.

Edited by Greg Wann, 27 September 2011 - 06:05 PM.


#7 Greg Wann

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Posted 27 September 2011 - 06:33 PM

Did you see the Cosma Ray that John Teresi built? I made those parts. I do not heat the mold for the bubble top parts. I have learned to be patient and they usually turn out great. I do use Price Driscoll Ultra 4 paintable mold release. I have used this spray on the bubble mold too. I spray it on and wait about 30 minutes and then take a paint brush and smooth it out. I am probably fortunate to be located in a low humidity area. I have tried the Novus stuff. There is just no comparison. The BMF polish is just much better!

http://smcbofphx.pro...play&thread=388

Here is a link to the mold creation of the Cosma Ray.

Edited by Greg Wann, 27 September 2011 - 06:38 PM.


#8 Chuck Most

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Posted 27 September 2011 - 07:25 PM

I do have to say I wouldn't mind doing what he was doing wrong on that second windsheild- it has a pretty realistic 'delaminated' glass look to it!

#9 dannyi

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Posted 28 September 2011 - 10:09 AM

I have made more attempts with the windshields but not for awhile now. I got a hold of Alumilite by phone and Smooth-On by e-mail. Except for a couple of different steps both were about the same. Both suggested preheating the molds. 120 degrees for no less the 15 minutes but no more then an hour. Pressure pot @ 45 to 60 PSI. Alumilite did suggest a Platinum cure silicone instead of tin cure. I did try that with little success. I did find out that leaving the mold in the pot for 3 days did reduce the air bubbles to almost none. But I was still getting hazy part and sometimes soft parts. I have tried Smooth-On 'crystal clear', Smooth-On 'epoxAcast 690 clear' and Alumilite 'clear'. They were all measured by weight, haven't tried by volume though, and haven't used any type of mold release.
I appreciate the suggestion though, thank you!. Haven't totally given up on it yet but I've gotten busy enough now with my resins(knock on wood!), that I can't really tie up my pots for 3 days anymore. Have thought about getting another pot strictly for the windshields, and might just do that now that you guys have offered more suggestions and sparked a renewed interest in it.
Again, thank you guys, I'll let you know how the next ones turn out. Would like to get the process down to where 90% or more turn out good. So far my success rate is pretty bad....

#10 Kris Morgan

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Posted 28 September 2011 - 11:22 AM

Danny, If you are just worried about doing windshields,,have you thought about getting a vaccum forming machine?

#11 Greg Wann

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Posted 29 September 2011 - 08:04 AM

One other thing I learned to do from experience. If there is any sticky resin left in the mold I take a plastic shoping bag and push it firmly into the goop. It pulls free from the mold and sticks to the bag so it won't damage your mold. I have scratched the important surface of the mold rendering it useless to me. You might still be able to get a free can of mold release as a sample from Price Driscoll. I think Jeff the Time Machine resin guy told me about it.
If you are doing serious casting in an area where humidity is a problem you might buy a dehumidifier for your room. Just an idea, it's a step I would do.

Greg

Edited by Greg Wann, 29 September 2011 - 08:07 AM.


#12 Art Anderson

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Posted 29 September 2011 - 12:07 PM

Hi,
Check and make sure that your clear resin is compatible with your silicone. Most clear resins will not cure against tin based silicone. Tin based silicone is usually blue. Platinum based silicone is used with clear resins. Platinum silicone is usually clear. If the part doesn't cure and stays sticky until you remove the first surface, this is more than likely a compatiblity problem.

Brian


When I was resin-casting, I investigated clear resins. For starters, polyester resins (chemically the same stuff that is the basis for the catalyzed putty we modelers have come to use, also same as fiberglas resin) don't work well with any sort of silicone RTV, as the catalyst (hardener) tends to leach into the rubber, leaving the surface of the clear sticky for all intents and purposes, forever.

That leaves clear polyurethanes. The best of these are "water" or "optically" clear, but they do require special handling. I never had a problem with these clear resins curing properly against "tin-cured" RTV, but they take special handling. Most of the really high-quality optically clear polyurethanes are slow curing, and emit CO2 as they begin to kick, or set up. The only way to prevent CO2 bubbles in the clear parts is 2-fold, from my experience: It takes a vacuum chamber to literally suck the CO2 out of the still liquid, but mixed, resin, and then to prevent any subsequent bubbles from forming, a pressure tank capable of holding at least 75psi for a couple of hours or so. The last thing is the addition of heat, at least low heat.

I found that when I pre-heated the molds used for headlight and taillight lenses, that heating the molds to at least 150-degrees or thereabouts before pouring them hastened the cure dramatically, and after removing the filled molds from the pressure tank, baking at 150-degrees for about an hour ensured that once cooled to room temperature, the finished parts were rock-hard.

Now all this is based on experience 1993-1999, so it's quite possible that clear polyurethanes have changed since then. Also, it is possible, I am sure that higher-tech clear polyurethanes have been developed that require platinum cured RTV.

Art

#13 Art Anderson

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Posted 29 September 2011 - 12:11 PM

Hi Danny,
Are you still trying the clear? Try mixing it 1to 1 by volume instead of by weight. I do resin casting. I made the parts that John Teresi has been building. I have been getting better at using the clear resin. I recently discovered that the clear resin I bought from Alumilite and Aeromarine products are the same brand. Alumilite says to mix it by weight and Aeromarine says to mix it by volume. I am a bit confused by this mixed information. I have better luck mixing it by volume. I pour out of smaller containers that are lab grade bottles. Make certain it is mixed very well. Make a good two part mold. Pressure cast it and do not open for at least three days. Making the bubble tops for the Cosma Ray that John built is easy to do now that I have learned not to touch it for awhile. I have a forum that I post a lot of my resin work on. Email me if you still need help.

Greg



Greg, early on in my resin castng time, I made the call to the manufacturer of the resin I was using, finally got patched over to one of their chemists/engineers, to get a conversion for the resin-to-catalyst mix from weight to volume. That worked very well for me--and I learned to use that from then on, contacting suppliers for that info for whatever product I was using. It's MUCH easier than constantly measuring by weight, especially since I (just as a suspect, most others) didn't have a super-accurate scale for weighing out the two parts.

Just a thought.

Art

#14 dannyi

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Posted 29 September 2011 - 02:00 PM

Kris....at one of our club meeting Jeff had mentioned that he had a vacuum forming machine and that it worked well for him. It's definitely an option to consider.

After reading everyone's comments, I believe my main problem is the mixing ratio's. I do have a scale but like Art said, it's not super-accurate. Going to try and obtain a conversion that Art also mentioned to mix by volume next time and see how that works out. I'm also going to try a higher pre-heat temperature and a longer time in the oven. Both companies said that because of the thinness of my part that pre-heating was a must but the temps and time varied depending on who I talked to. The humidity here is bad but the room I work in is air-conditioned, so I don't think it's a huge factor. Leaving the castings in the pot for 3 days at around 50 psi definitely took care of the bubble problem. Considering the pre-heat, lack of high humidity and pressure pot, all being good steps in the process, it has to be the mixing ratio's. hadn't thought about using volume, just tried to use the weight ratio's recommended by the company.
Again, thank you guys. Your suggestions have sparked a renewed interest, I'll keep you posted on my progress........Danny

#15 Greg Wann

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Posted 30 September 2011 - 07:03 AM

I too can conclude about a scale to do the weight measurements. I bought one of those little electronic jobs cheap off of Evil Bay. It has a 500 gram max witch is not bad but would shut off in the middle of my weighing process. And mostly give a different reading every time the same container of whatever was placed on it. Another thing I would suggest you try to do is get a lab type plastic beaker. a 25 ML is a good choice. They are smooth inside so resin is easy to mix They are small. I did take my medicine cup I got from my first Alumilite start up kit and measured out 2.5 ML of alcohol. I poured that in my 25ML beaker and marked a line with my exacto knife. I did the same with the teaspoon measurements. I use some 50 ML size ones also. Those little medicine cups to me are problematic. How much do I dislike them? Let me count the ways.

1. They are thin and flimsy.

2. They don't have a pour spout like a nice beaker does. I found it to be helpful.

3. As wonderful as they are for having many types of measurements the lettering is raised on the inside surface and there are little raised things in the bottom to make them easier to come apart when they are stacked. This a place where unmixed resin can possibly cause problems and the free Starbucks coffee stirring sticks will catch as I am stirring and cause resin to flip out of the cup.

4. I'm thinking!

OK the downside to using an expensive beaker.

1. You will need to keep it very clean with alcohol after pouring resin. If you forget and it cures on you, you will have a terrible time getting the resin out. Spraying some mold release in the cup and letting it set for awhile before you mix the resin in it will help if it cures and not effect the resin. You want the carrier or whatever you call it to gas out before mixing resin in the beaker.

2. there is an expense of keeping alcohol and TP on hand for keeping this tool clean. It is an important tool.

3. You must be certain to actually get the bottom edge of the beaker clean. The area where the side and bottom meet is sharp and not rounded so making certain that no resin can get there and cure. The free Starbucks coffee stirring sticks will find it by dragging on it if it is there and will splash resin out.

Why do I go to all this trouble? Because I make really good parts. How do I know I make really good parts? Because I have some great guys in a couple of model clubs here in the valley that tell me I do. The other really interesting reason to me is that I have been showing my resin work on another forum pretty much since I started and oddly enough is that I get no criticism. Hey, I'm still learning. I see guys show there model builds on here and get beat up over them. Bob Peoples (RIP) introduced me to Mike Hanson a professional model builder in Mesa. Mike looked at the parts I brought and he was really happy and told me my parts were Modelhaus quality. That made me feel pretty darn good too. I have done some work for him. Since a lot of people want to know what is involved in the part making process I decided I would post my work and become a lab rat.

It really sucks Gregg closed the joke thread. I had a couple of good stories to tell.

Edited by Greg Wann, 30 September 2011 - 07:38 AM.


#16 dannyi

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Posted 12 January 2012 - 06:19 PM

...well guys I finally got some good results. These were cast with Alumilite Water Clear. Getting an accurate scale made all the difference. These were done in tin cure silicone molds preheated @ 200 degrees for 30 minutes. That temp and time might be a bit overkill but I wanted to make sure they were plenty warm enough. They were then put in the pressure pot @ 50psi for 48 hours. I might be able to de-mold them sooner now that I have an accurate mix but I didn't want to take a chance on that either. Still have a lot to learn about casting clear resin windshields but feel better now that I've had some success.....thanks for all your help fellas
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#17 Len Woodruff

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Posted 13 January 2012 - 03:14 AM

Hey Danny what are the windshields being cast for? One looks like a speed boat?

;)

#18 Greg Wann

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Posted 13 January 2012 - 05:33 AM

WOW! Those do look really good. Congrats on your efforts.

Edited by Greg Wann, 13 January 2012 - 05:33 AM.


#19 paul alflen

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Posted 13 January 2012 - 07:19 AM

CONGRATS DANNI, I KNEW YOU COULD DO IT!! JUST LIKE THOMAS EDISON, TRY IT TILL YOU SUCEED ! GOOD LUCK PAUL

#20 paul alflen

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Posted 13 January 2012 - 07:22 AM

DANNI , NOW YOU CAN MAKE ANY RARE WINDSHEILDS! YOU JUST NEED A GOOD MASTER COPY TO CAST OFF OF ! OPENS UP A WHOLE NEW MARKET FOR YOU!!!