I've got a straight sided lentil press, and every bead I've made in it has broken in half... I'm getting really annoyed with it.
I'm batch annealing, so could that be the problem? Yesterday I even had one which went through the cooling process - into a tub of vermiculite straight from the torch and left for some hours - I got it off the mandrel no problem, then went back about 5 minutes later and it was in two pieces. It's frustrating. I don't have the problem with round beads - or not often.
Any help greatly appreciated.
Anne
Anne, are you pressing the glass to where it is thinner than the width of the mandrel? this is the usual reason for cracking
How big is the lentil? could be too much glass to cool in vermi or blanket.
Shaping your bead with a press does put a lot of stress onto it. Certainly I had more lentil cracks when I was batch annealing. There's something about the shape which seems to induce stress somehow.
You can minimise the stress by returning the bead to the flame once you've shaped it in the press. You should do this anyway to flame polish out the marks made by the press. Obviously you need to be careful becuase if you heat up the bead too much you'll lose the shape.
The other reason is that the press will strip a lot of heat away from the bead which causes a lot of stress. You will need to replace that heat by going back to the flame after pressing. Remember stress is primarily caused by the inside of the bead being at a much higher temp than the outer surface. To minimise stress you must also minimise this temperature difference.
You can try flame annealing your lentils before you put into vermiculite or fibre blanket. Do a search for flame annealing on here - there's a thread somewhere. Note that flame annealing does'nt actually anneal the beads but will go some way to reducing the stress.
Make sure you focus some heat along the mandrel on both sides of the bead when flame annealing before putting in the vermiculite. I used to manage lentils quite well when batch annealing - have you got your vermiculite warm - I found it helped. Also, may be worth considering some of Manda's annealing beads (again as Sal says they don't actually anneal but they slow the rate of cooling which is what you're after). Also avoid having your vermiculite in a metal container as it conducts the heat away.
Kazx
I batch anneal and I do lose the occasional lentil, but not that many. I try to ensure I heat the bead well after I have 'finished' it, then waft it in the back of the flame for a few seconds and then count about 15 seconds ish before I put in the vermiculite. Pressed beads are the worst when batch annealling, that's for sure.
HTH.
And ... if you're not already using skinny mandrels, maybe switching to them could help, then the 'wall' of glass around the mandrel will be a bit thicker and hopefully stronger.
I use a blanket and batch anneal, and as has been said I re-heat after pressing, and heat the mandrel too. The breakages I get are always from admiring the bead for too long before I put it to bed.. ::)
Thanks for all the advice ladies. As they say, tomorrow is another day, so keep your fingers crossed for me......
Anne
I significantly reduced my lentil casualties when going from vermiculite to a fibre blanket. I rarely get cracked beads now and I batch anneal. Xx
check the glass is compatable ..i had a problem with this when starting out .......dont check the sleeping lovelies to often and i batch anneal the next day ? ...i had more success with the blanket too
good luck ...it will just click into place ..honest ;)