help and advice needed for casting.

[jas46]

Hey everyone
I new here and to pen making but not to using the acrylics I just make other things with it lol
I am wanting to start casting my own blanks as in the UK the choice is limited.
I was thinking of starting with Polyester resin but I have tried to use it for my uses and it's just too brittle where as aluminite resin is perfect it's softer and less brittle.
my problem is I have the cash to set up for aluminite but don't want to spend loads to find out I'm no good at it or can't do what I want with it, flip side I don't want to spend a small amount of cash on polyester resin to find out if I like it and have blanks that I can't use....

I have every intention of pen making as well just not yet

so is there any way to make polyester resin less brittle and more like aluminite and any advise for my situation welcomed.
Thanks
Jas

 

[ssalvage]

If you are running into a problem with PR being too brittle, I would suggest you verify how much catalyst you are adding.
It has a fairly reasonable margin for error, however you do need to add the proper amount of catalyst in proportion to the ambient temp, amount of resin used, the thickness of your pour, etc.
Sounds to me like you might be putting too much in there.

I personally prefer to err on the side of too little catalyst. It may take a bit longer to fully cure that way, but it prevents me from having exploding blanks. :good:

 

[jas46]

Thanks ssalvage
I've not started casting yet, got my first lot of pr today lol
I was asking as I bought some pr blanks from a bloke who mixes and I lost probably 1/3 of a blank just by tapping it and didn't want to go into mixing pr if it wasn't suitable for my application.
but I ended up saying stuff it and bout some anyway as I will be making pens soon anyway lol
So when you say amount of catalyst to temp I'm assuming then that temp has a big issue with how things turn out as mine will all be cast I my shed which will be cold.

Thanks

 

[ssalvage]

Thanks ssalvage
I've not started casting yet, got my first lot of pr today lol
I was asking as I bought some pr blanks from a bloke who mixes and I lost probably 1/3 of a blank just by tapping it and didn't want to go into mixing pr if it wasn't suitable for my application.
but I ended up saying stuff it and bout some anyway as I will be making pens soon anyway lol
So when you say amount of catalyst to temp I'm assuming then that temp has a big issue with how things turn out as mine will all be cast I my shed which will be cold.

Thanks

Not sure what kind of PR you are using, but it should come with instructions that should be consulted for specifics.
That being said, PR cures based on heat. There are two ways of achieving sufficient heat to allow it to cure, chemical and ambient.

Chemical - Simply adding more than the recommended amount of catalyst will increase the internal heat in the PR and force it to cure. This is not the best idea, because the trade off is that you end up with very brittle PR.

Ambient - Ideally, you want to add the proper amount of catalyst, and pour your PR when the ambient temperature is between 70*-80*. This will allow it to generate the correct amount of heat internally, and cure in a more stable and use-able manner.

If you are going to be using your shed, I would recommend having a thermometer handy, and invest in a small heater to raise the ambient temp when it is too cold. If that isn't possible, what some people will do is make a small "curing cabinet" with a heat lamp so you only have to control the temp in there.

 

[efrulla]

You can buy Alumilite in quarts and that is what I suggest for all first timers. Part B has a shelf life and you more than likely won't go through a gallon of the stuff while learning. I don't know about the UK but here in the states you can buy Alumilite at Hobby Lobby and other hobby and craft stores.

 

[jas46]

Nope no instructions came with it but I have tried to make my first block in pink with black lol
I mixed up at about 1% hardener but I think I mixed the black in to early as it started to blend with the pink, but it took nearly 40 mins to I think the term is gell lol.
for a first go I'm happy as I learn what not to do for the next one lol and I'm hoping it will turn ok and look semi decent
I have read that adding more catalyst makes it more brittle so I under the 1% I'd rather have to wait longer than have it brittle.
I have a small heater in my shed to will give that a go
to be fair this order was a test to see if I can actually make a working blank before I invest more money and I think I may have been bitten by the casting bug lol and pen making, I'm ordering some kits up tomorrow night lol
I looked at aluminite but from what I've read you need a pressure pot that's something at the moment I'm not going to invest in, until I get seriously into casting then I will get the setup
I will get some pics up later on for you guys to see my first mess lol

Thanks

 

[jas46]

It may look a pink mess but I'm sure well it is a pink mess lol
Will have to wait and see what I holds within

 

[Curly]

In addition to the warm box you can heat your PR resin before adding the catalyst in a warm water bath. Run hot tap water into a shallow pan and set the mixing cup in it and let it warm up. Do not do this with Alumalite. An ultrasonic cleaner with a warming element is even better as it will help remove bubbles in the resin. If you are careful stirring the added hardener you won't add bubbles to the mix. Next day if the outside of the cured resin is tacky a short time in a toaster oven on its lowest setting will complete the cure. Don't take it back into the kitchen.

 

[jas46]

Cheers curly
I've got to buy a new ultrasonic as mine died but I'm gonna make a heater box from my old vivarium heating gear.
I'm going to do another mix tomorrow, how long do you guys leave it before you mix the two colors ?

 

[Curly]

You're welcome. Can't give you an answer on when to mix the colours because we've only done clear casting of imbedded objects like watch parts.

 

[Terredax]

First, I think you will be surprised when you cut into that "pink mess".

Next, it's my opinion and experience only, as we never actually tested Rockwell hardness, but the belief of resin becoming brittle from too much catalyst is not entirely correct. With the small amounts of variation in the amount of catalyst needed for such small casts as are used for pens, the brittleness is negligible.

We have exceeded 150 degrees on casts and there was no detectable difference in the brittleness. The catalyst is used to initiate the reaction of exothermic cross linking. The heat created isn't determined by the amount of catalyst (the amount of catalyst determines how rapidly the reaction begins), it is related to the amount of resin in the cast.
Doing a "post-cure" in an oven has the same effect as the exothermic reaction, but is an extension of that reaction. The "post-cure" is not required if the cure temperature is achieved.

When using epoxies, the reaction isn't determined by the amount of catalyst, but rather the type of catalyst.

There are also resins that use heat range catalysts similar to automotive coating products.

This is just my opinion, please interpret it accordingly.

 

[jas46]

This is the turned result of my first pour

Ironically my second pour went bad and very bad,I tried waiting to mix two colors this time and we'll left it about 30 seconds too long and it wouldn't mix Grrr but hey atleast I now know not to hesitate

 

[jas46]

I'm not sure on the brittleness vs amount of catalyst I have only just started lol but thanks for the info mate, I'm sure in time I will get a better understanding of it all.