Leadlighting Tutorial Lesson 6: Advanced Glass Cutting - methods for difficult shapes.
The purpose of this exercise is to take notice of the techniques, how and when used. Simple cuts are mastered very quickly, adhering to correct methods; this lesson is to look at the best methods of the more difficult cuts that can be encountered. Easiest cuts are shown first, progressing to the harder shapes.
Draw these shapes and practice these cuts on clear glass so that you will become familiar with how to cut them when or before using stained glass.
Where possible, depending on the nature of the cuts, make all score lines of the piece being cut prior to penetration, rather than one score line, then one penetration – as it speeds things up. (Remembering what has been said about a hot and cold score line - lesson 1.) But if there is a difficult cut involved, it is better to concentrate on getting it out first by itself. On all shapes containing internal curves, cut this curve first. By allowing more waste than usual, if you fail you may still be able to move the glass and try again. This applies to any and all shapes except the following, which has particular techniques.
POINT CUTING: Points are encountered everywhere with variations to those described.
It doesn’t matter whether scoring away from or towards the point, but always penetrate towards the point. If a double point exists, a point at both ends, (eg. a leaf) penetrate from the centre after making both score lines. Penetrate in the right sequence in all instances.
If you were cutting a crescent shape, which consists of both an internal and external curve - after scoring and penetrating both score lines, ALWAYS remove the internal curve first.
Sometimes depending on the shape, you need to think about which score line to penetrate first to successfully remove the waste and save the point. On the first diagram below, one of the points has a definite hook to it, which is a potential problem.
There are always three key things to cutting any shape – scoring, penetrating, and separation. Scoring has already been dealt with. Penetration has only partly been dealt with; this will address it more fully. The aim of penetration is to make separation for some shapes easier and in these cases penetration is done GENTLY. (As mentioned before penetration only goes part way through the glass.) Glass can be turned over and pressed over the back of the score line to penetrate but we don't want to press so hard that it separates immediately if we can avoid it. Press in the middle of the score line, not at the edge and the penetration will run away on both sides of your thumb towards the edge or points. Chase the penetration to the edges.
Remember when you may have practiced penetrating the ‘Harbour Bridge’ in lesson 1 from the centre on the reverse side with your thumb - you would have learnt how hard to press to start the penetration i.e. not too hard nor too soft, just enough pressure to ‘see’ it happen.
The aim is to penetrate so that the waste pieces are still connected to the principal shape. I find it best to do this on the cartoon on the bench, not on any padding. Of course different glasses will require different pressures, so it's gently does it until we see it happen - that way the waste is still connected, which is what we want.
By achieving this we have a better chance of saving the points, particularly on the side near the hook because the waste (number 2) is supporting it. On the first diagram there are the numbers 1 & 2, which mean: The first score line is number 1, the second is number 2 (simple I know but bear with me.) Just make sure you don’t overrun the score line on the second score at the hook, finish on it – not past it. Penetration is the next step, which is done on the reverse side from the middle as mentioned, in the same number sequence.
If we simply use the running pliers on either end, after scoring both score lines, the score line will take the least line of resistance and run down the wrong side (2) and it may even separate before we get a chance to stop it. In which case we will lose the point on the right hand end and possibly the other, because this is the side we want to be still connected to the shape to protect the point. (I know, I’ve mentioned that twice.)
In the paragraph below POINT CUTTING, (above) I've mentioned to penetrate after making both score lines. If you only make one score line you can certainly easily remove the waste, but now that piece of glass is gone and no longer supports the principal shape at the points. There is now a very considerable risk of losing the point when you try to remove the waste after making the second score line. Exactly the same result will occur if you were to remove No. 2 first, but with a much higher risk when you try to remove No. 1 second.
So, if you first cut the shape as directed by the numbers, then completely penetrate both score lines and everything is still holding together, you have a 99% chance of retaining the points. I'm sure you can now understand why penetration is always done as gently as possible in these types of curves - if you can manage to partially penetrate both score lines so that the waste is still connected, separation is simple in all instances.
Separation happens after penetration, either with your hands or grozing pliers from the centre in the same sequence. (1 then 2.)
Now look at the points, they’re still there!
The next shape is a 4-pointed star and you often see this shape in traditional work where it has this shape on two right angle lines that cross over each other and separating four pieces of glass. Cut a square of glass that is a little larger than the opposite points as in the diagram. (You may think you could reduce the amount of waste by cutting a smaller square so that it just covers the shape diagonally, but the pieces you are going to remove will then be smaller and not as easy to penetrate as a larger square as in the diagram.) Score in the fashion shown, the first score line is the ‘complete’ score line, i.e. from one side of the glass to another side in any direction. (See score line number 1 on diagram.)
The second score line starts at the edge and finishes with the wheel just IN the first score line at the point on the cartoon. You should hear a ‘click’ as the wheel joins with the number 1 score line. The third score line is exactly the same. The fourth or last score line is merely ‘joining the dots’ so to speak. The next step is to penetrate all four score lines as carefully as you can. Here again once you have it penetrated completely with the waste still connected, you are 99% done. Hold the shape in one hand, thumb on top, index finger under and use grozing pliers or your fingers to separate each waste piece. It won’t be difficult.
You can find this shape in the photo of the tulip mirror in Lesson 1.
The next shape looks like a comma in glass and again it is found in traditional work as a lick on the end of a curved shape. Cut from a piece of glass about 30mm larger all round for the best result. I’ve seen many different ways to cut this shape, but this is the best and easiest way. Start by scoring the shape completely in the direction of the arrows all the way round. Unless you are a contortionist, you will have to stop scoring part way round. Carefully move the cartoon, making sure the piece being cut doesn’t move on the cartoon so that you can continue scoring (one hand on the glass, the other moving the cartoon.)
You’re probably thinking I’ve only got two hands, how do I keep the cutter on the glass?
You don’t, you can see the score line from the oil, where you couldn’t go any further - simply put the cutter wheel on the glass just behind and slightly to the side where you stopped, slide it over until you ‘feel’ it drop into the score line then continue. You should be able to complete the cutting in two moves, but it’s ok to do it in three.
You’ll notice on the diagram there are two sets of numbers; the circled numbers in red refer to penetration sequence. Once you’ve penetrated completely, following the diagram, you’ll also notice the shape is trapped by the waste.
On the face (smooth) side where you first penetrated, run two separation score lines in to the wanted shape at a tangent (being careful not to overrun the score line.) Either by hand or running pliers, penetrate the separation score line into the shape so that the waste piece numbered with an UNcircled number 1 (in blue) is separated FIRST.
As in the leaf shape discussed first, by leaving the waste piece, uncircled number 2, still connected to the principal shape you know you’ve protected the point. Now penetrate the separation score line to separate the uncircled number 2. Lastly separate the uncircled number 3. There you have it – a perfect comma!
Whenever you encounter points of this description just think about which side to leave on to save the point - opposite the more difficult side. A teardrop is another similar shape but without the hook and is also very common in traditional leadlights. Use exactly the same technique, except after penetration and running the two separation score lines in at a tangent, it doesn’t matter which waste side you remove first as it’s a mirror image.
The hardest waste shape of all to remove, simply because if you fail the score line runs away into the area you are wanting to keep. The smaller or deeper and narrow determines how difficult, the best way.
· 1. Score the shape.
· 2. Penetrate completely. (tumble glass, press on top of curve to penetrate first, then chase the penetration out to the edges.)
· 3. Put a wedge, or V score line in, don’t overrun the curve. Provided you have penetrated completely, the wedge is prevented from running through the curve.
· 4. Shock the wedge out by tapping under, remaining segments are easily separated.
· 5. Leave glass oversize on the edge nearest the internal curve and trim off later. (Saves edges breaking away.)
(See more about point 2 using grozing pliers to help remove the waste in Lesson 1 under using grozing pliers.)
If the shape you are cutting has a number of internal curves in it, remember to always cut the most difficult curve first and make the cut from a much larger piece of glass than required so that if you fail you may still be able (hopefully) to move the glass and try again. After cutting and separating the difficult cut first, it's now out of the way and the easier cuts can be made with less worry.
CUTTING CIRCLES OR OVALS:
A circle cutter can be used, or if cutting glass freehand, score half at a time, as in the left diagram below. Use a compass to draw a circle on the cartoon.
Turn glass over and press all round on the score line to penetrate. Then turn back to the face side and run four score lines out to the edge of the glass, STARTING at the extremities of the circle so that you don’t overrun the circle. (Make two score lines back towards you first from one side, turn the glass for the other two. Don't be tempted to make only one cut in the middle, either side of the circle.) Gently penetrate each score line into circle or oval from both sides and ends will easily separate. Remainder is easily removed.
CUTTING A HOLE:
A circle cutter can be used or score accurately freehand. The bigger the hole, the easier it is. Again use a compass to draw the circles on the cartoon about 15mm apart.
Mark the glass where you will FINISH scoring with a felt tip pen. Score every circle, the outer circle is the finished size; the two inners are ‘safety’ circles.
If you are scoring freehand you would start at the bottom of each circle (the same as for a circle) and finish at the top at the pen mark for each circle.
Turn the glass over and from the back at the pen mark, penetrate all 3 circles. (The reason for the pen mark is because scoring freehand you have a 50% chance of hitting the score line at this point exactly, you may miss it by a millimetre or so. If you were to start penetrating where you started to score, when the penetration gets to where you finished, and because they may not have lined up, you could easily loose the lot. By starting the penetration at the pen mark, even if you missed joining up perfectly it will join up now.)
Turn back to the face side and score across, inside the centre circle several times, forming a grid pattern. (Keep these score lines WITHIN the circle.) Tap from underneath over a bin so the glass pieces are instantly disposed of. (Be careful of pieces flying up as you tap, protective glasses should be worn and it’s surprising how hard you need to tap.) Begin tapping under each score line from the centre and working out to the inner circle in both criss-cross directions. This is causing the penetration, do not tumble and press to penetrate, it’s too risky and it's here you will see how easily shells can form by tapping under the glass as mentioned in Lesson 1. As you progress each score line toward the inner circle, ease up slightly on tapping pressure as the score line runs into the penetrated inner circle. Once this is completed come back to the centre and tap until the first square falls out, when this square is released the rest becomes easier.
After removal of the centre grid area, remove any feathers for safety. Cut V score lines into the first circle – about 50mm. apart. Again, tap from underneath on each V and each segment will fall out. Repeat for the final circle. You now have a hole.
There is another way that has evolved from this way, but I won’t describe it as I think this is the safest way.
Some reasons why you might want to cut a hole.
Sometimes putting an exhaust fan in a bathroom is an afterthought. If you know how to cut a hole it may be cheaper to put the fan in the window rather than through a wall, exhausting water vapour into the ceiling cavity is not a good idea. Of course it's easier if you remove the glass first.
In modern designs it is very interesting to see a ‘free-standing’ circular piece of glass in a large background piece. It certainly creates wonder, how was it put in there all on it’s own with no break lines. See photo lessons 2 & 7.
Here’s the trick.
You first cut the hole, then complete the cutting on this piece of glass for its finished shape on the cartoon. (Try to have this hole 6" or 150mm in diameter for ease of completion - the larger it is the easier it is.)
Then cut a circle 5mm smaller in diameter than the hole using a different glass. A large clear Rondell or iridescent glass is very effective. If using a Rondell, cut the hole 5mm larger as the Rondell is already made.
Use a square 2.8mm U lead to wrap around the circle and another one inside the hole. Place the leaded circle into the leaded hole then wire brush and flux for soldering.
I usually solder it at this stage so that it goes in the job as a completed piece.
Remember in soldering (step 7) when soldering a long join on an acute angle? Use a similar technique here, placing small amounts of solder every 5-8mm or so. Re-fluxing and using the soldering iron like a sewing machine – up and down, up and down (not dragging) reasonably quickly so as not to burn the lead and moving along 4-5mm at a time until you’ve finished. Don't pause every time the iron touches the lead at all during this moving along process as you risk burning the lead, it is on and off and the lead is heated up uniformly as you move slowly along. As you solder it should be forming a molten river behind where you have soldered gradually solidifying to form what looks like a continuous lead. If the leaded circle fits into the hole snuggly there shouldn't be any trouble soldering as described, but if is a little loose solder can sometimes fall through the gap, which will simply need adding more solder as you go. Just keep the roll of solder handy so that you can immediately apply without slowing down.
That’s a secret to keep your friends guessing for some time.
SETTING OUT AND DRAWING AN OVAL:
You may want to make an oval mirror. This is a simple, easy way.
Distance between A & B = C to B1 and C to B2, i.e. if distance AB was 300mm, C to B1 and B2 is exactly the same. (Use a ruler or large compass for this.)
Place a nail on points B1, C and B2.
Tie a string around these nails.
Remove nail at point C.
Place pencil inside string and draw the oval. Cut a groove in the pencil for the string.
Making leadlight mirrors.
As mentioned before in Lesson 2, mirror is impossible to see through and again, the best method to cut the mirrored pieces is to cut clear glass templates as if the clear glass was going to be used in the mirror, IE. using the technique described and cutting the shape slightly smaller all round. When you are finally satisfied with the template, trace around it with your cartoon pen on the face side of the mirror and cut ON the line - you don't want the mirror to be smaller than the template. Store the templates in case you ever need to make another mirror. If you need to slightly grind mirror make sure the table of the grinder is free from grit and grind with the face side down.
When making a mirror the best outside lead to use is a Y13. It is the strongest lead you can use and it also has the appearance of a metal frame around it. It is also substantial for soldering the wire twist-ties on the back side of the flat section. You make two of these from 150mm lengths of copper wire folded in half. Where folded, place a phillips head screwdriver blade inside the fold and wind one side of the wire around the blade of the screwdriver so that the wire is twice around the screwdriver. Using a Phillips head screwdriver, it's easier to remove from the wire after twisting the copper wire it's full length. You now have a fixture to hang the mirror from. Before you solder it to the back edge of the Y13, the tie must be tinned with solder so that it will adhere to the lead. Grip one end of the tie with a pair of pliers and coat the tie with liquid flux using a cotton bud. Coat half of the tie with a small amount of solder from your iron then repeat for the other half. Now that the ties are tinned, wire brush the Y13 where you will attach the tie and apply some stearine flux to the lead then solder the ties to the lead using plenty of solder. Your aim is to swamp the ties with solder to bury them deep so that they won't pull free.
If the mirror is an oval shape, when putting a Y13 on, use the same technique as putting the outside lead on a circular leadlight (see lesson 5) but put the first half on so that it goes over the top lengthways, which makes a nice even curve, then put the bottom half on in the same fashion. It's easier to put the leads on lengthways but it can look a little 'pointed' at the top and bottom, simply because you don't get a nice even curve at the top and bottom.
When you hang a leadlight mirror on a wall that contains stained glass as well as mirror, a lot of the intensity of the colour in the stained glass is lost because there is no light source behind it. A very effective way around this is to buy stained glass that has had a mirrored surface put on it, which gives an amazing result and is well worth the extra expense of the mirroring. Sometimes leadlight shops carry small amounts of stained glass to sell that has been mirrored - if your supplier doesn't have any, he should know where to have it done for you. Hartley Williams in Brisbane carry a range of mirrored stained glass - you can look at their catalogue on-line but it doesn't really show the true effect, you have to see it to appreciate it. An alternative is to tape some silver foil behind the glass, but it is nowhere near as good as mirrored stained glass. Try this first to see if you like it.
Another alternative is to use opal glass. Opal glass doesn't work with mirroring, it works on its own by reflection, so using opals is a cheaper and sometimes better alternative.
A simple way of protecting the mirrored surface in a leadlight mirror is to spray the back of it with hair spray before puttying up on the face side. This helps to protect the cut edges of the mirror and is a seal against moisture ingression, which is the cause of black rot. There are commercial products for this but hair spray is a cheaper fix and just as good.
Glass selection for leadlights.
There are so many different glass types, colours and textures to choose from when making your leadlight and by varying the colours and particularly textures, will help to bring it to life. During the day, because the light source is outside the building, the colours are more intense from inside the building. The opposite happens at night - when a light is on in the room, the colours are displayed only on the outside of the building, making them more interesting from outside. But there is another benefit that is revealed at night on the inside and that is the glass that is textured, (being on the inside) really stands out much more than it does during the day, so the more texture you can incorporate into your leadlight, the better it will look at night, even though it is dark and without colour.
But just a word of caution, sometimes a part or parts in certain designs can look better with an opal glass to get the desired effect and again there are many multi-colours and textures as well in opals - and during the day they work well. However, it's a different story at night. Because opals are a very dense glass and work more on reflection than penetration, opals jump out at you at night. The colours in the opals showing up by reflection and the rest of the leadlight appears dark and without colour and this can be an odd effect on the inside. It's better if you can use a plain stained glass to get the effect you want but sometimes there isn't a choice.
One clear texture to avoid is the Australian clear Cathedral as it has a very 'milky' appearance. Specify either the European or Chinese clear Cathedrals as they are much clearer or cleaner in appearance.
© 2010 John Jackson