Casting diamondback blank trouble

[Padre]

I have cast many diamond rattlesnake skin blanks in crystal clear Alumilite. I sand the tubes, then I CA glue the skins on the tubes, wait overnight, then place one of Charlie's molds in the pressure pot and pour in cc Alumilite. The Alumilite is mixed well. I then pressurize for 1 hour at 60 psi.

After turning the blanks I sand with 320, then go through the entire micromesh inventory. I am using WET pads to do this. I then polish with HUT plastic polish.

The blanks are coming out cloudy (see attached pics,) not completely, but in spots and I have no clue as to why. Picture one is one side of the pen with some cloudiness. Picture 2 is the other side of the pen where it is mostly cloudy. When holding it in your hands some of the cloudiness is shiny and sparkly.

1. Could it be tiny air bubbles?
2. Could it be water from the micromesh seeping into the blanks?
3. Could it be the HUT plastic polish?
4. Could it be the crystal clear Alumilite?
5. Could it be the CA glue that gets on the outside of the skins?
6. Could it just be me?:tongue:

Any help would be greatly appreciated.

 

[ed4copies]

I can't see well--ever.

But, I would guess that you are not letting the CA cure thoroughly and it is "offgassing" in the pressure pot.


BTW, ALL the ones you mention (except #6) are ALSO possible. (Sorry)

 

[TomW]

I have given up using CC alumilite with snakeskins. I think the CC just gets too hot.

Tom

 

[Padre]

Ed, it is alumilite, how long should I wait until I pour it over the tubes?

 

[Padre]

Did you go to water clear or PR?

I have given up using CC alumilite with snakeskins. I think the CC just gets too hot.

Tom

 

[ed4copies]

Chip,

I have NO knowledge of alumilite.

BUT, I don't cover CA for several days, if I use it for ANYTHING!! It can offgass for quite a while (days), depending on ambient temp and humidity.

 

[TomW]

Did you go to water clear or PR?

PR.

Tom

 

[surveyzo]

I had the same thing happen to me. I figured I was letting to much heat build up from the sanding.

 

[KDM]

I only started casting a few days ago. I can't see very well but the photos look like stress fractures. Does it look like long, thin cracks? The resin will probably shrink as it cures. Probably quite significantly. If these are cracks, it might be because the plastic has shrunk too tightly onto the tube.

 

[TomW]

I only started casting a few days ago. I can't see very well but the photos look like stress fractures. Does it look like long, thin cracks? The resin will probably shrink as it cures. Probably quite significantly. If these are cracks, it might be because the plastic has shrunk too tightly onto the tube.

One feature of Alumilite is minimal shrinkage when it cures. That's why it's so good for worthless wood casting. The negatives are heat during cure, reaction to minimal amounts of water.

Tom

 

[ed4copies]

Unlikely to get stress cracks in small castings.

THAT problem shows up in BIGGER castings, usually!

 

[seamus7227]

Just my .02 worth: it has been my experience that when there is too much heat on these snakeskins, they tend to shrink just slightly, I used to use a toaster oven to do the final cure with PR and have since discontinued that due to the exact same thing happening. Now, after no longer using the toaster oven, i just let them cure on their own. I also MM to 12000 using the wet sanding method and have no problems, however, I seal the ends of the casted blanks with thin CA so that I dont have any problems. Just an extra safety measure for me. Hope this helps

 

[Padre]

That's a great tip, thank you.

Just my .02 worth: it has been my experience that when there is too much heat on these snakeskins, they tend to shrink just slightly, I used to use a toaster oven to do the final cure with PR and have since discontinued that due to the exact same thing happening. Now, after no longer using the toaster oven, i just let them cure on their own. I also MM to 12000 using the wet sanding method and have no problems, however, I seal the ends of the casted blanks with thin CA so that I dont have any problems. Just an extra safety measure for me. Hope this helps

 

[its_virgil]

Alumalite is a good product but not for snake skins. Polyester resin is a much better product for snake skin blanks. DO NOT post cure snake skin blanks in an oven. The result will be exactly what you are getting with alumalite.
Do a good turn daily!
don

 

[MesquiteMan]

Does anyone know the temperature that PR achieves when it is curing? The reason I ask is because I DO know the temp of Alumilite, both CC and Water Clear and I have a hard time believing that the problem is because Alumilite gets hotter when it cures. I have an infrared surface thermometer and have checked numerous batches of Alumilite in the various formulations and the hottest I have seen with a big block was 165 degrees. Is PR that substantially cooler? I know it gets hot too but have no idea what temp since I do not use it. I also do not do snakeskins!

I heard a more plausible explanation from someone a while back. Their theory was that PR is more brittle and thus does not expand when the kit parts are pressed in and the brass expands a little. Alumilite has a MUCH higher elongation factor, meaning it will stretch further before it breaks. The EF for Crystal Clear is 8% where I believe PR is about 1% though it is hard to find the technical detail on PR. That is what make folks thing that PR is harder than Alumilite when in actuality, Alumilite is just a hair harder than PR with a Shore D hardness of 80 with PR coming in at 78. Anyway, the theory is that the Alumilite stretches a more and allows the resin to separate at the weak point, the bond between the skin and resin which causes the silvery look mainly on the ends.

 

[TomW]

Curtis, I have never had a CC Alumilite snakeskin get to the point of installing hardware. All got the silvery look, or the skin pulled completely away from the tube by the time I removed them from the pressure pot. Checking the blank made it clear no pen would result.

Tom

 

[its_virgil]

1. Could it be tiny air bubbles? Yes, and big ones...lots of them
   
2. Could it be water from the micromesh seeping into the blanks?I don't think so..I've never had wet sanding damage blanks...but I don't use alumilite.
   
3. Could it be the HUT plastic polish?No.
4. Could it be the crystal clear Alumilite?Yes, not much success from several others using alumilite for snake skin casting.
   
5. Could it be the CA glue that gets on the outside of the skins?No, I often coat skins with CA prior to casting with poly resin.
   
6. Could it just be me? Yes, and me and most of the others who make snake blanks have had this problem...or something similar. I;ve had much worse casting the same way every time. Excellent results and then WHAM!

And, I don;t think heat is the problem. Too much heat usually causes cracks or fissures, at least in poly resin. Post curing snake blanks is a no no. I know that alumilite was used in the blank discussed in this thread, but I hope some of my comments will be helpful.
Do a good turn daily!
Don

 

[Padre]

Don,
Thank you for this. It gives me hope that I will, someday, cast a good pen blank. I never heat post cure, so I know that isn't an issue. I have some water clear that I might try, but I also just ordered a gallon of PR. I know it stinks, but I don't want to waste anymore snakeskin.

1. Could it be tiny air bubbles? Yes, and big ones...lots of them
   
2. Could it be water from the micromesh seeping into the blanks?I don't think so..I've never had wet sanding damage blanks...but I don't use alumilite.
   
3. Could it be the HUT plastic polish?No.
4. Could it be the crystal clear Alumilite?Yes, not much success from several others using alumilite for snake skin casting.
   
5. Could it be the CA glue that gets on the outside of the skins?No, I often coat skins with CA prior to casting with poly resin.
   
6. Could it just be me? Yes, and me and most of the others who make snake blanks have had this problem...or something similar. I;ve had much worse casting the same way every time. Excellent results and then WHAM!

And, I don;t think heat is the problem. Too much heat usually causes cracks or fissures, at least in poly resin. Post curing snake blanks is a no no. I know that alumilite was used in the blank discussed in this thread, but I hope some of my comments will be helpful.
Do a good turn daily!
Don

 

[ed4copies]

Don,
Thank you for this. It gives me hope that I will, someday, cast a good pen blank. I never heat post cure, so I know that isn't an issue. I have some water clear that I might try, but I also just ordered a gallon of PR. I know it stinks, but I don't want to waste anymore snakeskin.

Bad news. The only way you will not waste ANY snakeskin is to not cast them. There is a "waste factor" no matter how many you cast successfully. As Don says, sometimes it doesn't work, doing it EXACTLY as you did before.

(Have you heard me say ambient temp and humidity????)

 

[Padre]

Yes, I have read many times.:biggrin: I should have said "waste any more than necessary!" :wink:

Bad news. The only way you will not waste ANY snakeskin is to not cast them. There is a "waste factor" no matter how many you cast successfully. As Don says, sometimes it doesn't work, doing it EXACTLY as you did before.

(Have you heard me say ambient temp and humidity????)

 

[PR_Princess]

I don't have any experience with Alumilite. But we do know that urethane resins work well with other organic compounds....So, why NOT rattler????

This kinda makes me wonder if there isn't a chemical reaction taking place here between the urethane resin, the skin and/or the chemicals that the skin was preserved with. (Water may not be the only thing that urethanes are sensitive to.) Maybe Alumilite or a chemist can chime in?

Meanwhile, Padre if there is anything that you feel I help with after you get your PR, LMK!!:biggrin:

 

[Padre]

Dawn,
Thank you for this kind offer! I will let you know, as I anticipate I will need some help. I've read a lot of the articles on IAP, but doing is different than "book learnin'"
:biggrin:

I don't have any experience with Alumilite. But we do know that urethane resins work well with other organic compounds....So, why NOT rattler????

This kinda makes me wonder if there isn't a chemical reaction taking place here between the urethane resin, the skin and/or the chemicals that the skin was preserved with. (Water may not be the only thing that urethanes are sensitive to.) Maybe Alumilite or a chemist can chime in?

Meanwhile, Padre if there is anything that you feel I help with after you get your PR, LMK!!:biggrin:

 

[workinforwood]

The skin is a bit oily, Alumilite does not stick well to oily surfaces, just like people have experienced with certain worthless wood attempts. Can't say I blame the product there either...would you expect paint to hold up on a dirt road? Alumilite also does not stick to CA very well. CA will stick to alumilite great, but not the other way around. CA is a hard slick surface and Alumilite does not stick well to hard slick surfaces. Alumilite is a urethane resin, not glue. To paraphrase Mike at Alumilite, if Alumilite was glue I'd be a millionaire! So you need to not have CA on the outside of the skin..good luck with that. You need no oils on the skin..that's possible to do. Then problem 2 is that although the skin may feel dry, skins attract moisture very easily and the moisture content in your skin might just be a bit high for Alumilite..too much moisture makes a white cloudy resin..we've all seen that many times before, and you are in Conneticut which is near the ocean, so humidity can be a tougher battle out there. And finally, there is the whole speal Curtis offered..and that is all complete logic. With PR, when you install a part in a tube, the part squeezes in and it either fits perfect, or the PR blank cracks. Usually there is just enough space between the tube and the blank, and for a cast tube such as snake skin, there is no space, but the skin itself can squeeze down a touch when a part is installed and the PR will not budge, so then you are ok. With Alumilite, you push in the part, the tube expands..but because the Alumilite has some stretch factor, the skin does not squeeze in between, but rather it pushes on the alumilite which stretches itself off of the skin, leaving behind a void that looks like a cloud. All of these are reasons why people use PR for snake skins, not alumilite. Even the Alumilite people can't figure out how to successfully cast snake skins with their product. I love Alumilite, my resin of choice..this is just one of those examples where the product is not right for the job at hand. It's an expensive lesson.