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After cutting 5/16" thick slices from 2 ea. 3/4" sq. X 10" pattern bars, I arranged them in a 7 X 7 square design. The pieces were cleaned meticulously but not otherwise prepared. They were generally very square and fit together nicely except for the 'top' which was slightly crowned (see Wet Belt Sanding, below). I fired them to slightly greater than a contour fuse at 1450 deg. (Spectrum 96). Along all of the internal edges, and particularly at the internal corners, there developed a noticeable 'crud'.

Is there a process whereby I can remove this (sandblasting, overspray)? Is there a technique or heating cycle whereby I can avoid this?

I've done a few pattern bar pieces. I too have noticed the crud.

It seems that every surface that has been in contact with fiber paper or kiln wash (three of the edge surfaces of your PB slices) need to be ground or blasted before using.

I avoid the crud by sandblasting or grinding the bottom and sides of my PB block before cutting it into slices. It seems that blasting or grinding both work.

Larry

Sure, you can sandblast the crud off and then use an overglaze and firepolish.

I dip my saw cut pieces in etch bath for 10 minutes - wash throughly then apply super spay and fire away - they always come out nice.

Hi-

Could you explain the etch bath - etching cream mixed with water?

Thanks,
Pat L.

Hi Pat:
You can purchase the etch creme at any hobby store, got mine at Micheals. Sorry, can't remember the brand name. I pour the solution straight from the bottle into a tupperware container. Then I place my glass in the container and leave sit for 10 minutes or so. Then I remove, wash and dry.

Wear rubber gloves, and the solution smells.

Kim

you can also get scum from the ground edges coming to the surface.

Charlie - I suspect that's exactly where it's coming from. Other than using etching cream, do you have any suggestions how I might treat/prepare the squares before fusing so that I might avoid this? - Sandy

lisa allen is the pro at this. you might ask her what she does.

what i do is grind the edges with my grinder head to get it even, and then touch up the edges with my wbs using a very fine grit belt. it appears that the cutting/grinding leaves small holes in the edge, and this is a devit nucleation point.

also, i leave my tiles in water after cutting on the tile saw, so that the holes don't dry with powder in them. if they dry out, it's harder to get them clean again.

In lieu of a wet belt sander, consider getting a couple or three different grits of diamond handpads ($10 to $15 each) and making a few passes over each edge like it was a sanding block. Keep them wet and rinse often.

http://ecprod.abrasive-tech.com/product ... dSubCat=83

Tony

I'm VERY appreciative of all the feedback I've received. I don't want to complicate the matter, but (in the interest of more accurately painting the picture/describing the problem) ...

The faces of the sawn squares (which 'suffered' the tile saw) are nicely polished after firing - its the perimeter of the squares (the original exterior of the bar) which seem to have leached some scum which, to a modest but very discernable and ugly degree, largely surrounds each individual tile. Does this change anyone's advice?

Please NB "Appreciation" (above)