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 crack !
Author: pirkwein 
Date:   05-21-02 18:47

question for experts in acrylics:

yesterday my sister dropped my 2.75 in."acrilyc" from the gardentable on concrete and a star-shaped-1/4-in.-crack appeared. 2 questions now:

1. does I have to do something to avoid it for cracking more ?

2. can it really be an acrylic or is it somthing else? I think it seems a littlebit blue,so it can be a policarbonate, but that can be wishfull thinking.Are there any "objective" methods to check it ?


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 Re: crack !
Author: Matte Black 
Date:   05-22-02 01:31

I have so many little dings, cracks and scratches in my acrylics the local juggling club reckoned I should be locked away for abusing pretty toys. No, nothing you can do to repair it, it's not going to spread, and I would see no reason to doubt it's an acrylic. If anything, polycarbonates are supposed to be harder.

Welcome to the club. Still got the Stunt Double, Ferret?

-=Matte=-


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 Re: crack !
Author: ICU812 
Date:   05-22-02 04:28

in my experience polycarbs scratch more easily. I haven't really abused my acrylics though. if you want to check if it's a polycarb, hold it up against a blacklight. If it glows, it's a polycarb, if not, it's acrylic. You might as well just keep practicing over hard surfaces with this ball now that it has a mark on it. Now you don't have to worry anymore about ruinning it. It's already f*cked.

Jacques

"We are what we repeatedly do. Excellence, then, is not an act, but a habit."
-Aristotle


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 Re: crack !
Author: Axl Rose 
Date:   05-22-02 05:33

Hell ya! Look at your ball and say hello to Biff, the ball that will remain with you for the rest of your life! (I call mine Biff, you can name it whatever) You can now feel free to throw that ball as hard as possible against the pavement, drop it off tall buildings to see how high it bounces, and practice like a mofo anywhere you want with it. Believe me, that ball will become your best friend. And not only will you see your skill increase as you allow yourself to be more daring without the fear that you will break that pretty thing, but it is also nice to have something so pretty to throw around when you are pissd off. Good luck and remember: Chicks dig scars.


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 Re: crack !
Author: GReg 
Date:   05-22-02 15:42

I will repeat my statement from before. Polycarbonate does not glow under black light. This is a Myth. There are plastic additives that make it glow, that these additives can be used with any plastic.

This is a weird myth and it's still wrong.

-GReg


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 Re: crack !
Author: Marz Kelly 
Date:   05-22-02 19:52


GReg, not to contradict you as you are, for the most part, correct, however...

One or to of the CHEAPER polycarbonate casting solutions will, in fact, glow under a black light, this is due to the general level of impurities, most that do have impurity levels of 5-7 percent. It can be quite pretty, but the glow of a polycarb ball is proof that the ball is even cheaper than you might wish. Good polycarbonate casting compounds do not glow under UV.

Marz Kelly


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 Re: crack !
Author: GReg 
Date:   05-23-02 02:50

I agree with you that this is caused by an additive, but the glow is from a catalizing agent.

***START RANT HERE***

You can use this agents that make plastic glow unintentionally with Acrylic, PolyCarb, Acetate, PETG (sp?) and several other plastics. It does not show that the plastic is polycarb. The plastic can be many things besides polycarb and still react the same way under UV.

This is a pet peeve of mine. Somehow everything that glows like this is Polycarb. This is not true. You can not tell from the glow if something is Polycarbonate.

There are several reasons you probably would not want polycarb for a contact juggling ball, but softness is not one of them.

There are also several agents for use in plastics that make the plastic glow like this. I know the complete details of only two of them, but I am aware that there are at least 5 agents that will react like this. According to the paperwork I do have, not all of them weaken the plastic. They each do different things, but they all cause the plastic to react under UV.

Also it is not necessassarly a cheaping factor or a not "good" factor. One additive acts as a release to make the plastic work more easily, Most of the stuff that makes the plastic glow is to protect the plastic from Photo Degrading (it reflects UV instead of absorbing it so it glows, it prevents the plastic from turning yellow and brittle in the sun.). Several are combined products. Materials wize they all cost more than the basic plastic ... which also has additives in it. Actually I am not sure you can get raw material without some sort of additives in it any more. Everything is so specialized. Most acrylic today is dishwasher and microwave safe thanks to an standard additive that I don't think you can even get the plastic without :) not that I would put an acrylic ball in a microwave or a dishwasher.

Hmmmm.. Thats not true. Coming to think of it I have put one in a microwave ... but I'm not sure I would reccomend it.

Let me stress that this is mostly just a personal pet peeve about semantics. You can't judge the plastic by the glow. The glow does not make it or does not ... not make it polycarb.

***END RANT***

On other fronts, I have an idea about an internally lit acrylic ball. Prototypes are about 6 weeks away. I might have something really cool for CJC2002. Thanks to Robin to kick me in the but to start working on this project again. I'm have some limited success, so I am hopefull that this will actually work in production.

-GReg


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 Re: crack !
Author: Marz Kelly 
Date:   05-23-02 19:09


I find that I must agree with all of the points you have made... on a slightly funny note, the two clear casting mediums that I have used that did do this are no longer on the market (The company that made them is now out of buisness.). It was not my intention to state that all polycarb balls golw under uv, nor that anything that glows must be polycarbonate and apologise if I was in this wise misunderstood. Also: thank you for the information concerning stabalisers, most of the knowledge I have has been gained from expermintation, and I did not know that.

Ta,

Marz Kelly


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 Re: crack !
Author: GReg 
Date:   05-23-02 19:49

No worries. This rant was not directed at you. Somewhere on this site it definitively states that the UV effect means that the ball is polycarb. It has just grated on me.

So please don't take this as a rant geared towards you.

-GReg


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 Re: crack !
Author: mdamelio 
Date:   05-23-02 22:53

that place on the site would be the tips section, as well as numerously mentioned in the forums.

~Mickey


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 Re: crack !
Author: Lance Coombes 
Date:   05-24-02 18:52

I took that tip out so it should not show up anymore. Ya happy now, Greg?!?! Heehee. ^_^

--
Imagine that there is some clever signature here.


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 Re: crack !
Author: pirkwein 
Date:   05-24-02 21:13

but my ball glows under blacklight, what is it then ?

and if hardness isn't a reason to refuse polycarbs, what is it then ?


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 Re: crack !
Author: GReg 
Date:   05-24-02 21:15

Lance Coombes wrote:
>
> I took that tip out so it should not show up anymore.
> Ya happy now, Greg?!?! Heehee. ^_^
>
> --

> Imagine that there is some clever signature here.



:) I feel all powerfull now.
*Place recording of thunder here*

-GReg


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 Re: crack !
Author: ian pugh 
Date:   05-28-02 19:45

if you have a polycarbonate ball, count yourself lucky. i have yet to find a plastic manufatcurer or supplier who stock large diameter polycarbonate balls. they all tell me polycarbonate is more expensive than the acrylic, and for an item that is decorative, why would they use a more expensive product to make it. i'd love some polycarbonate balls, but i just cant find them. where did you get yours?


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 Re: crack !
Author: pirkwein 
Date:   05-29-02 16:48

they told me that the acrylics sold by mr babache are actually carbonates (i think remy wrote it down once, maybe ask her), I don't know it's true, but if so, those balls are easily to find. If you really can't find them where you live drop me a line (pirquin@hotmail.com) maybe I can help you.


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