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Coldworking with Loose Grit

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Coldworking with Loose Grit

Postby Chris_Petrauskas » Mon Jun 10, 2013 4:22 pm

Watch the Lesson at:
https://videos.bullseyeglass.com/videos/coldworking-with-loose-grit/

Please discuss and comment in this thread.

Thanks!
Chris Petrauskas
Bullseye Glass Co.
Portland, Oregon, USA
http://www.bullseyeglass.com
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Re: Coldworking with Loose Grit

Postby clgpwr » Mon Jun 17, 2013 10:39 am

I have a question. Would it be possible to use a stainless steel base rather than sheet glass?
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Re: Coldworking with Loose Grit

Postby charlie » Tue Jun 18, 2013 7:30 am

it just needs to be very flat and not be porous. glass is ideal. i get scrap thick glass at window/shower door shops for free, or very cheaply at yard sales (think glass dining room tabletops). you can get scrap granite pieces at custom counter top places (sink cutouts or other small scraps) usually very cheaply or free, if you convince them that tossing them your way keeps it out of the landfills and is cheaper for them as they don't have to pay disposal costs.

if it's not flat, then it would be very hard, if not impossible, to use.
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Re: Coldworking with Loose Grit

Postby Katie » Thu Jun 20, 2013 10:49 am

Have always used machinery to cold work and would like to try this. Where is a good source for purchasing the loose grit?
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Re: Coldworking with Loose Grit

Postby lbailey128 » Thu Jun 20, 2013 2:20 pm

I understand the loose grit method and have used it a bit with good success. However, I am a little puzzled by the sequence in the video where sections of the flat lip of a dropped bowl are scored, broken off and the bowl taken to the loose grit station. At first you can see that the ragged edges are there as it is beeing worked in the grit. Then those edges are suddenly gone in a following section, as if grinding vertically in the loose grit removed all the glass remaining from the scored/cut lip.

That's a long way down, does the video suggest grinding in loose grit to remove the remaining horizontal lip?

Could this same result be achieved more quickly by scoring/cutting as shown and then grinding down the remaining outside sections on regular rotary grinder? I assume that if this is possible you'd need to be careful not to stress the sides of the bowl against the grinder.

Thanks
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Re: Coldworking with Loose Grit

Postby alicia59 » Thu Jun 20, 2013 7:12 pm

on the video the loose grit that was used was 80, 220 and 400, Why would they not use 120 after the 80 instead of jumping to the 220 grit??

Ali C.
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Re: Coldworking with Loose Grit

Postby charlie » Fri Jun 21, 2013 7:14 am

Katie wrote:Have always used machinery to cold work and would like to try this. Where is a good source for purchasing the loose grit?


look up sandblasting or abrasives in your yellow pages. most largish cities will have some industrial place that sells to this crowd. you can buy it over the interweb too, but shipping will probably be as much as the material.
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Re: Coldworking with Loose Grit

Postby charlie » Fri Jun 21, 2013 7:17 am

alicia59@bellsouth.net wrote:on the video the loose grit that was used was 80, 220 and 400, Why would they not use 120 after the 80 instead of jumping to the 220 grit??

Ali C.


no rhyme or reason. on my loose grit flat lap, i use 60, 120, 220, 400, 800, cerium, or basically doubling the previous step. some day i'm going to get a cork floor tile and try that after 800, as cerium is so expensive now.

skipping one step just means it takes longer at the next step than if it weren't skipped.
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Re: Coldworking with Loose Grit

Postby lbailey128 » Wed Jun 26, 2013 3:23 am

lbailey128@gmail.com wrote:I understand the loose grit method and have used it a bit with good success. However, I am a little puzzled by the sequence in the video where sections of the flat lip of a dropped bowl are scored, broken off and the bowl taken to the loose grit station. At first you can see that the ragged edges are there as it is beeing worked in the grit. Then those edges are suddenly gone in a following section, as if grinding vertically in the loose grit removed all the glass remaining from the scored/cut lip.

That's a long way down, does the video suggest grinding in loose grit to remove the remaining horizontal lip?

Could this same result be achieved more quickly by scoring/cutting as shown and then grinding down the remaining outside sections on regular rotary grinder? I assume that if this is possible you'd need to be careful not to stress the sides of the bowl against the grinder.

Thanks


Would someone from the BE team respond here please? Very curious and others had the same question about the video......

Thanks for the feedback
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Re: Coldworking with Loose Grit

Postby marykaynitchie » Wed Jun 26, 2013 8:56 am

Hi all,

Where do I buy the abrasives?:
These should be pretty easy to locate. Here are some suggestions:
1) Your local art glass dealer.
2) HIS Glassworks is an excellent source for smaller quantities of abrasives.
3) Bullseye Glass now carries a selection of loose grits at our Resource Centers and in the Bullseye Online Store. http://bit.ly/12koQwf
4) There is usually a supplier in larger cities catering to industrial applications and rock polishing for the rock hound. (For those of you translating: rock hobbyist or rock aficionado!)

From Jim Weiler, who teaches this method and was the main scriptwriter:

Why did I skip 120 grit? The short answer is, I didn't have any! The long answer is that there isn't a magic bullet for coldworking strategies, much to the dismay of all my coldworking students. By skipping a grit I am indeed spending more time at the higher grit that I otherwise would need to. But the loose grit is pretty efficient to begin with and I probably saved time by not having to clean my work station and piece and set up for three grits instead of the two I used. So in the end it was efficiency coupled with the fact that we don't currently have 120g in house. On a side note, it is easier to see evidence of prior grit marks when skipping a grit. The white pock-mark dots jump out at you a little bit easier.

Please note, that Bullseye technicians do not reply to every question on the Forum. We also depend upon and deeply appreciate the Forum members who contribute information and advice. Because our way may not be the only way to do something, it is best for all of us to consider advice from all of you who have a wider range of experience than we can offer.

In this case, I was able to get some information from Jim. I am happy to share it, and I hope you find it helpful.

Mary Kay
Mary Kay Nitchie
Bullseye Glass Co.

Subscribe to Bullseye kiln-glass videos at
bit.ly/BullVideos
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