I've a new tank all ready to start setting up and need a few extra bits of glass to cover the tank and to form a filter box inside. Normally I go to the glazier for these, it takes 5 minutes and I get all the bits I want the right size for about 2 quid.

This time I've got heaps of glass from a recently dismantled greenhouse and since the glazier will be shut anyway over the xmas period I decided to cut up the greenhouse glass to size myself.

Having always avidly watched the glazier do this on many occasions I thought piece of cake and got started. Measured up, used a glass-cutter to score along the line, matched the line up with the edge of the table and applied firm pressure to the overhanging bit.
The glass broke but the break didn't follow the line. Three attempts so far before loss of light stopped play, three wasted bits of glass.

Any glass-cutting experts out there able to suggest where I'm going wrong? The only thing I can think of is that my table isn't flat enough and it needs to be flat right up to a very sharply defined edge so that the stress in the glass is focused along the line and nowhere else. If I'm right about that then I'm on a hiding to nothing since I haven't got a surface like that outside (and I ain't gonna try this in the kitchen!).

Any tips or suggestions (other than give up and wait until the glazier re-opens)?

Thanks Sawnee, looks like the odds are stacked against me here since;

• The glass is old (probably 40 years)
• It is cold (had to scrape snow off it),
• and it is poor quality greenhouse glass

I used an old door as a work table and did try using a piece of timber as a straight edge on one of my attempts. Problem is the tolerance in the straightness can't be guaranteed so don't know if it's in contact all the way along the line.

Next off I'll try warming it up after it's been scribed, might try the matchstick trick too.

I'm not giving up yet, there's a lot of glass to get through and it would otherwise just be dumped.And if I fail to get even one good bit out of it t least I'll have lots of little bits rather than a few large sheets which will be easier to transport to the municipal skip!

Hi cutting glass is all about conifedence.{i have cut more glass than i care to remember - most successfully}
Right first off - a dead flat surface,a decent glass cutter{be honest how old is it?}A perfect straight edge {preferably a peice of wood}
Right now how to do it.
Place glass on flat surface,measure where you are going to cut and place straight edge along the line{use a felt tip} Now with the glass cutter 'score' along the line{the cutter should make a nice 'scratch' and make a scoring noise as you move it along - this should be done in one smooth movement with even pressure}Now remove the peice of wood and there should be a nice 'scratched' line the whole lenght{this is very important - espcially at the edge of the glass}
Now turn over the peice of glass - place the straight edge along the score line and with one hand holding the peice of wood firmly use your other hand{with a glove on}pull upwards and it should{in theory}snap cleanly along the scored edge..
Now this is best if glass is on the small side, if larger peices are being cut use the peice of wood and push downwards to break the glass with the scored edge uperrmost.
Now a peice of advice when your glass is cut to size - rub down the edges with aluminium backed sandpaper or a sanding stone as cut glass is EXTREMLY sharp!
Good luck.
I once spent the day cutting glass for a chippy{as he had never cut glass} i cut over 100 peice's of glass to 8 x 12 inches out of a 8 foot by 4 foot peice of glass that was fun!?!

I would invite James round for a cuppa, and show him my uncut glass collection, di

Sounds like getting the scribed line right in the first place is the key, and probably where I'm going wrong. Very detailed procedure Stingy, I'm studying it very carefully. The glass cutter is brand new FYI!
I'll persevere, maybe I'll crack it maybe not, might end up following Dave's advice in the end but I'd rather not let this beat me! Anyway I've plenty other uses for all that glass besides just this one tank.

CORNERS!!!!!!!!!!!!

Straight from a cracker that one

Sorry Stingy, didn't quite get round to replying to your last post (29 Dec).

Gave up on the greenhouse glass for the time being and used some thicker stuff I've had lying around for ages which was originally secondary double glazing in the house. This was a bit more successful, at least I got the one bit I really needed urgently to make my filter box (now installed) and another bit that didn't quite break along the scribed line but close enough to make a cover for the tank. There's a bit more of this stuff left to play with and I'll have a go at making covers for other tanks one of these days, there's too many gaps in all my existing covers. Maybe I'll have another go with the greenhouse glass once I master the art with the easier stuff!

Hadn't thought of cutting corners for cables etc before - hmmm.....
Would be a lot easier just to drill holes for these I think although that means cutting moulded plugs off the electrical bits and fitting new ones.

so far.....

carborundum stone (sorry for the spelling)