Alumilite and Ambient Temp

[mark james]

The last time I cast Alumilite it was warmer in Ohio. I have some blanks from the Ohio Chapter that I would like to cast this week, so I would appreciate some advice.

What are the lower temperature limits of casting Alumilite Clear.

Note: I do warm my molds, but my equipment is in an unheated garage, so the Pressure pot will be about 50-60 degrees. And...possibly lower if it gets cooler this week.

I have had no trouble with my casts at 40 psi for 60 minutes.

Thank you to any help with the fickle weather in Ohio!

 

[mark james]

Bump... My garage is getting co:coffee:lder!

 

[Leatherman1998]

Data sheet shows Demold Time at 75 Degrees F (100g mass) is 45-60 Min. Curtis would probably know for sure but I probably wouldn't go below 50. It has no smell though so why don't you do it in a washroom or semi heated room?

 

[mark james]

Data sheet shows Demold Time at 75 Degrees F (100g mass) is 45-60 Min. Curtis would probably know for sure but I probably wouldn't go below 50. It has no smell though so why don't you do it in a washroom or semi heated room?

I have had reactions to different chemicals; skin dermatitis - I need/want to be careful. (Once you get it, it usually will not go away, and further exposure will make it worse.). No smell, means you may not be aware of what is in the air. Urethane sensitivity is still bad - even if it does not smell like PR/epoxy.

I did a trial cast in the garage just now (demolded 15 minutes ago) - 57 degrees in the garage; 40 psi for 60 min. a 2 Sierra mold, humidity at 44%, came out crystal clear (foil blanks)!

I have put in a second cast - tubes from my Ohio Club Members. garage temp is at 56 degrees.

 

[Leatherman1998]

I have had reactions to different chemicals; skin dermatitis - I need/want to be careful. (Once you get it, it usually will not go away, and further exposure will make it worse.). No smell, means you may not be aware of what is in the air. Urethane sensitivity is still bad - even if it does not smell like PR/epoxy.

I did a trial cast in the garage just now (demolded 15 minutes ago) - 57 degrees in the garage; 40 psi for 60 min. a 2 Sierra mold, humidity at 44%, came out crystal clear (foil blanks)!

I have put in a second cast - tubes from my Ohio Club Members. garage temp is at 56 degrees.

Alumilite isn't a urethane though, its a polymer, if I remember correctly Curtis said the chemical strength of alumilite is low enough kids could play with it

 

[mark james]

I have had reactions to different chemicals; skin dermatitis - I need/want to be careful. (Once you get it, it usually will not go away, and further exposure will make it worse.). No smell, means you may not be aware of what is in the air. Urethane sensitivity is still bad - even if it does not smell like PR/epoxy.

I did a trial cast in the garage just now (demolded 15 minutes ago) - 57 degrees in the garage; 40 psi for 60 min. a 2 Sierra mold, humidity at 44%, came out crystal clear (foil blanks)!

I have put in a second cast - tubes from my Ohio Club Members. garage temp is at 56 degrees.

Alumilite isn't a urethane though, its a polymer, if I remember correctly Curtis said the chemical strength of alumilite is low enough kids could play with it

Kids may play with it (not mine without gloves...)... But it most certainly is a 2 part urethane. (sorry, my wife is a PhD. Polymer Chemist ).

 

[MesquiteMan]

Mark is correct. Alumilite is a urethane. Polymer is a very general term for anything made up of more than one monomer! Monomers and polymers come in all shapes and forms and are only related to resins in that resins are typically polymers!

When I said kids can play with it, that is the cured Alumilite.

As for temperature, I would not know! Being in Texas, my shop never gets below 55 degrees or so and I have not had any issues. I can say that in the summer time when the temp is higher and causes the Alumilite to set quicker, I keep my Alumilite in my shop refrigerator to slow the reaction down some. Never had any issues using it straight from the fridge.

 

[Leatherman1998]

Mark is correct. Alumilite is a urethane. Polymer is a very general term for anything made up of more than one monomer! Monomers and polymers come in all shapes and forms and are only related to resins in that resins are typically polymers!

When I said kids can play with it, that is the cured Alumilite.

As for temperature, I would not know! Being in Texas, my shop never gets below 55 degrees or so and I have not had any issues. I can say that in the summer time when the temp is higher and causes the Alumilite to set quicker, I keep my Alumilite in my shop refrigerator to slow the reaction down some. Never had any issues using it straight from the fridge.

Thx Curtis, must of been the part of class I was sleeping in xD

 

[mark james]

Levi and Curtis...
Thanks for the responses!

and.. I'm no Chemist! I just relay what SWMBO says! (actually, she is VERY interested in my casting with Urethanes!).

I will continue this thread for future reference.

So Far - Last run - Garage temp 51 degrees; 56% humidity; 61 Min at 40 psi.
Came out crystal clear - and HARD. Like it had sat and cured in warm temp.

So, I have another (final for tonight) run in at 50 degrees and 59% humidity.

I Love working with Clear! Very easy and user friendly.

I wil take Pics in a few moments of the first few runs. For us folks in northern areas, this may be helpful.

 

[Curly]

Pet stores up here sell electric heating pads for dogs, like an electric blanket. One in a box, with the pressure pot on it, and closed once the air pressure is applied, should keep it warm and toasty.

 

[mark james]

Pictures are a bit dark as it is late into the evening; however...

All three runs came out very clear and hard.

 

[robertkulp]

Pet stores up here sell electric heating pads for dogs, like an electric blanket. One in a box, with the pressure pot on it, and closed once the air pressure is applied, should keep it warm and toasty.

Be very careful when warming a pressure pot. Heat causes the air to expand, increasing internal pressure. If you do this, MAKE SURE you have a working emergency pressure relief valve.

You don't want it to go KA-BOOM!

By the way, I've also been thinking about it for this winter, too. I might build an insulated box with a light bulb (incandescent, not florescent) as a heat source and wire in a 120V thermostat to regulate the temp. I've heated dog houses in the winter with this method and it works really well. Just use a cover to block the light in a dog house, though.

 

[Sylvanite]

I cast using Alumilite White, RC3 Black, and Clear year round. My shop temperature gets as low as 45F (lower than that, and I run my salamander) and my castings turn out just fine.

I normally run at pressures around 40-60psi in a pot rated at 80psi. I have a pressure relief valve, but the seal tends to leak above 60psi anyway.

Regarding unsafe pressure with temperature rise, let's perform a though experiment. Assuming that the resin doesn't compress, and that air is an ideal gas, then the formula for pressure is "PV = nRT", or "P=(nRT)/V", where P is pressure, V is volume, n is the number of moles of gas, R is a constant, and T is temperature in degrees Kelvin. Since the volume, and the amount of gas are also constant, then pressure is directly proportional to temperature. If you fill the pot with air at 45 degrees Farenheit, seal the pot, and warm it up to 80 degrees while curing, then the pressure will rise by about 7%. If you started out at 60psi, then the final pressure will be about 65psi. That is not typically a dangerous pressure.

Now, when you compress air, the temperature will increase, and Alumilite curing is an exothermic reaction (meaning it releases heat), but not nearly enough to raise the pot temperature by 20 degrees.

Don't worry about shop temp when using Alumilite resins. The pot life varies with ambient temperature, but I haven't seen any effect on curing.

I hope that helps,
Eric

 

[mark james]

Hi Eric:

Thank you for the input! I kind of... followed your info, but my resident Chemist is on a beach - without me (work calls...). She flew the coup after a Medical Conference last week. Yup, I'm not the sharpest Skew in this family!

Yes, All of my runs went well, down to 48 degrees. Actually, I think the blanks came out harder than when I have done runs at higher temps in the spring/summer. These were not tacky, and very clear casts.

I appreciate all the above thoughts! Thank You.

 

[le_skieur]

Pet stores up here sell electric heating pads for dogs, like an electric blanket. One in a box, with the pressure pot on it, and closed once the air pressure is applied, should keep it warm and toasty.

Be very careful when warming a pressure pot. Heat causes the air to expand, increasing internal pressure. If you do this, MAKE SURE you have a working emergency pressure relief valve.

You don't want it to go KA-BOOM!

By the way, I've also been thinking about it for this winter, too. I might build an insulated box with a light bulb (incandescent, not florescent) as a heat source and wire in a 120V thermostat to regulate the temp. I've heated dog houses in the winter with this method and it works really well. Just use a cover to block the light in a dog house, though.

Robert,
My shop stay's at 57 to 60 in winter time
I confirm that a box heated with a light bulb, in my case I put a 100w in it and work great. Before doing that my blanks were tacky and now they dries perfectly. The pressure had increased by 1 or 2 pounds but I only cast at 45, no need for more. I cast with PR.

 

[Charlie_W]

Mark,
Can you have your alumalite in a heated area before using so it is room temp before starting? The hot box sounds like a good idea!

 

[mark james]

Mark,
Can you have your alumalite in a heated area before using so it is room temp before starting? The hot box sounds like a good idea!

Hi Charlie: Yes, I store the Alumilite inside my house, so it is at 68-70 all the time. I also warm my molds, and I took the pressure pot into the house for 1/2 hr before casting.

All has come out fine the past week. I made a 1" x 1" x 7" mold on Sunday and it is clear and very hard. Temp was 57 degrees and 52% humidity in the garage, but everything was warm. I cast at 40 PSI for 90 minutes (since it was a brick instead of a blank!).

Thank you to all the above for your thoughts!

If I do anything during the winter I will try the light, which will be an easy addition as I actually cast inside of a sandblasting box due to allergies - cumbersome, but worth the lack of a skin rash!

http://content.penturners.org/library/tools_and_jigs/casting_box.pdf