Cutting Mirror


SGF, Supreme Grumble Framer
Jul 9, 2001
Skaneateles,NY USA
I searched the archives, didn't come up with anything on this, so here's my question:

What are your tips on cutting mirror?


Depending on the weight of the mirror i.e. 2, 3, 4, 6mm you may need to cut it on the bench with a Tee Square and a GOOD glass cutter either a TOYO or a Fletcher glass cutter rather than on the wall cutter, the thicker the mirror the more resistance you will have when you snap it after scoring it, be careful, score on the glass side not the silvered side.

Bottom line there is no difference to cutting mirror than cutting glass, mirror is just glass with a coating on one side.

6mm mirror is the best of all for making mirrors it gives the best and truer reflection.

Get back to me if you have problems and I will go into things in more detail.
We've had good results with our Fletcher 3000, I score the mirror then squirt some napha (lighter fluid) onto the score this seem to run the score and gives a smoother edge.
I don't cut my own except small, thin ones. Am fortunate enough to have a friendly glass company up the street. I buy all mirrors from them except standard size beveled ones. If a customer has one they want cut down, I ask them to take it to the glass company and they will deliver to me for framing.

Please do tell us more about cutting mirrors. The 1//8 inch ones are easy, but 1/4 & up have been a problem for me. By that I mean I can't break them at all.

Thanks for your help on this.

Cutting Glass and Mirror

You will need:

· A FIRST AID KIT: Have a First Aid Kit handy, with gauze and some good tape.
· GLOVES: Gloves, preferably ones that glass can’t cut through.
· PROTECTIVE EYEWERE: Safety Eyewear is a good idea it can’t hurt.
· A GLASS CUTTER: Use best quality you can afford, the cheap ones are useless.
· A STRAIGHT EDGE: A selection of Tee-Squares are best.
· A WORK BENCH/TABLE: The Work Bench or Table will need to be as level as possible.

In case you did not already know, Mirror is Glass, with the silver coating sprayed on one side.

Mirror is manufactured in sheets of about 8 x 10Ft. it will then be cut to more manageable sizes by the glass merchant and it comes in weights of 2, 3, 4, 6mm it is unlikely that you will find mirror in imperial weights nowadays as most mirror comes out of China and the production equipment in China is generally metric equipment.

The thickness of mirror and glass is described as the weight of the glass as glass and mirror was in times gone by sold by weight.

Cutting glass or mirror is a little like cutting wallboard/sheetrock with a razor blade, cut the outside paper and bend it, it breaks where you cut the paper.

I learned to cut glass on a bench and have never mastered the use of my wall cutter for this task, to me it is frightening to have glass or mirror at face level, I know many of you have mastered the wall cutter and if you are conformable with that you will not need Tee-Squares or straight edges, I’m directing this post in the way I cut glass and mirror.

The work bench NEEDS to be as level (flat) as possible otherwise you will get a croket cut line and the glass/mirror will not snap properly, I have covered my bench with carpet this helps to take the unevenness out of the bench, special benches for cutting glass can be purchased I think they would cost from about $2500 to $20.000 depending on what you need.

Lesson 1: Have a very flat workbench or forget going any further, you will NOT succeed in cutting heavy mirror or glass without a good flat bench covered with a carpet or if you can get it the special felt that glass suppliers use on their benched.

Straight edges as glass is very smooth it is unlikely you will keep a straight edge from slipping, you could try covering one side of your straight edge with very fine wet and dry sandpaper it will reduce the likelihood of it slipping also the straight edge needs to be a strong one like the ones you have in the US for cutting sheetrock, light straight edges will flex and give an uneven cut. I have three Tee-Squares 30”, 48” and 72” these are quality Tee-Squares for the glass industry, these allow for very straight score lines on the glass/mirror that allows for good snap lines.

Lesson 2: Have a selection of Tee-Squares

Don’t skimp on your glasscutter, the cheap ones are useless for anyone that is serious about cutting glass/mirror. When you score the glass/mirror it makes a distinctive sound, so you must listen to it (turn off the CD player) if the sound skips so then did your score line, try filling in the skipped part before moving your Tee-Square, try a few practice cuts first. 2mm or 1/8” should be allowed on the measured size for the thickness of the head of the glasscutter.

Lesson 3: Get a good glasscutter and allow 2mm for the thickness of the head of the cutter.

Hold your Tee-Square firmly where you want to cut the glass/mirror to cut (mirror glass side up). The glasscutter scratches the outside surface of the glass/mirror. Hang the glass over the edge of the bench or slide the Tee-Square under the glass/mirror on the score line (scratched line) and bend down. That won’t work if you only cutting off a little, at least try cutting of 2” waste or more, hang your 2” over the edge of the bench after you have scored the glass/mirror and tap on the underside directly under the score with the blunt end of your glass cutter, tap lightly until you see it break just a little, line the score back up with the edge of the table then right at the little break bend the 2” down almost as if your twisting off the 2””. If you are cutting 4mm ¼” glass/mirror or more it will be allot harder to bend, you will have to tap the underside allot harder also, I would recommend you buy a pair of breaking pliers they are made specifically for breaking glass/mirror along the score line. The other way as I said is to slide the Tee-Square under the glass/mirror this is a bit difficult with mirror, as you cannot see the score line

Lesson 4: Be careful and practice first, allow enough waste for an accurate break.

Use gloves and protective eyewear and have a first aid kit to hand (you should have a first aid kit already if not you are being silly and possibly breaking the law).

Please be very careful the people who introduced me to glass/mirror cutting had a combined 300+ years of experience between them.

Another tip, if you buy your glass/mirror in the big sheets and do not have a straight edge big enough to cut it with, cut a 3” strip free hand off the sheet and use the straight side as a straight edge.

If safety is a concern for mirrors you could use the slide door mirrors that are used in bedrooms, this mirror has a safety backing, you cut and snap it in the way described above then you need to cut the safety backing with a razor blade or burn it apart but that’s for another lesson.

Finally beware there is a relationship between the size of glass/mirror to weight that you can safely use, again someone gave me the details but unfortunately I have miss placed the chart.

Take care.
Or . . .

Do what Sherry and I and others do and have your supplier cut it to size.

I DO appreciate Dermot's detailed instructions. He has a background in glass that makes me think he knows what he's talking about. But cutting large mirrors, to me, is like doing gold leaf. It's nice to know how to do it and I hope I never have to do it. (I know some of you do leafing and my hat's off to you, too.)

Thanks everyone!! I have mastered my Fletcher 3000, and I purchased 1/8" mirror cut down into a more manageable size than the large sheets they typically want to deliver. These things are usually bigger than I am! (5'2" is stretching it!!). I learn something new everyday from you guys and its great!


p.s. I love my Hot Press vacuum!
Ron and Sherry are right nowadays I have my supplier (the guy I gave the glass business sorry sold!!!! the business to) cut my mirrors all I do with mirror these days is cut an off cut down to size.

Best deal is to get to know your local glass guy they know what they are doing and will generally refer customers to you, now in my case the local glass shop also does some framing, they are OK but difficult to deal with, so I now go to the next town nicer people.
The part not addressed is the ability of glass to "heal" following the score. Also true of mirrors. The thicker the glass the faster it "heals" so you need to be faaaaasssssttttt!
Try popping a scored cut right away and then wait a minute and try another. BIG DIFFERENCE in the cleaness of the cut. Actually I think that being quick is one of the most important qualities a good glass/mirror cutter.
Could someone explain this thing I read about glass healing, I have run this past people who have many many years experiences in the glass business they wanted to know if I was…………MAD or had I lost my REASON.

I have seen this recently as a sample question in the brochure that the PPFA send out about the CPF exam, it makes no sense to me and I have cut hundreds of tons of glass and mirror in my time.

Is there some true fact behind this healing thing or is it just some urban myth.

Is this suspicion about cutting these things because most folks use the wall mounted cutters?I have always cut glass like Dermot on a bench and can say that I find it no trouble at all.Most of the glaziers I speak to say that the 2mm glass we use is the worst stuff to cut.If you can master cutting that then most glass cutting should be fairly straightforward.But if you are not confident about it then its best to farm it out to someone who is.
Okay, I've made a business decision. Starting Monday, I'm having Reynard cut <U>all</U> of my glass, especially the mirrors, and <u>all</U> of my frames. The shipping costs might be a little steep but everything will be perfect and I can chuck my sanders and my wall-mounted glass cutter.

Sorry, Reynard, I couldn't resist. No offense intended, but you do make us all sound pretty wimpy over here.


I personally enjoy the subtle differences in Dermot's posts vs. Reynard's posts. It reminds me of my times in Europe when I had the good fortune and opportunity to imbibe some of the best whiskies on earth.

When I first tasted Jameson whiskey, it was like eating the frosting off of a top notch dark chocolate cake! Smooth, full bodied, and one of the best sippin' whiskies I have ever tasted. I was asking directions from a local fella in Dublin and he took me to a tiny bar, I can't remember the name, started with a "K" I think but I wanted Irish whiskey and he got me a Jameson's.(I don't drink to excess, but I love to try nice things.) I have never seen Jameson's here in the states. I don't know if it is not imported or simply not carried by most of the local watering holes that I have visited in my travels.

Bushmills, on the other hand, gagged me when I first tried it. But, as was pointed out to me by a local Scot, I had no "feel" for the scotch. He said that you must acquire a "taste" for good scotch.

Sadly, I never did but the point of this reminiscence is that maybe you haven't acquired a "taste" yet.


A little correction Bushmills is an Irish whiskey it is made in the North of Ireland in a place would you believe called “Bushmills” it is considered to be one of the oldest distilleries in the world, it is very near Giants Causeway one of natures wonders of the world.

Now I don’t drink myself or at least I don’t take drinks of the alcoholic type and one thing I strongly recommend is that you DO NOT ATTEMPT to cut glass of any nature with a skin full of Jameson or Bushmills under your belt.

Do you pay well Ron?

I was being serious when I said I had no problem cutting and joining without the need for sanding.Maybe the sander finishes stuff better but I feel I am a fussy swine when it comes to turning out work and if it wasn,t right it wouldn,t be going out of my shop.

As for the whisky I have tried a lot of different stuff and was able to impress my brother in law by naming a particular brand of malt by taste alone.

Can I be your whisky taster too Ron? ;)
Having re read my posts they may come across as having been pretty arrogant.It wasn`t my intention to come over all superior.I was just brought up cutting glass the way glaziers do.Wall mounted cutters were not available and I have never used one so I don`t know anything about using them.As for mitre joints I have an accurate saw which is idiot proof.And the morso is set up right and cuts as it should.So no need for sanding.If the work coming out your workshops is good then it matters not a jot how it occurs.I knew an old boy who would only cut mitres by mitre box then finished them on a planing chute sort of contraption.It worked for him for his entire career.I get the same results as him in far less time by a machine which makes all his skills almost redundant.I am not claiming to be a wonder framer but the machines I use do the job first time.Nothing to do with me.I just get the blades sharpened now and again.
Originally posted by Dermot Cox-Kearns:
Could someone explain this thing I read about glass healing, I have run this past people who have many many years experiences in the glass business they wanted to know if I was MAD or makes no sense to me and I have cut hundreds of tons of glass and mirror in my time.

Is there some true fact behind this healing thing or is it just some urban myth.
Dermot, my friend,

I had been taught this phenomenon since I started in the industry 24 years ago, and was always a bit suspicious of it's truth. More recently I learned that there was indeed some truth to it, but also some controversy still existed among those glazier experts.

I decided to go to a reliable source for a definitive answer......I dropped an E-mail to a retired engineer at The Fletcher-Terry Company, Wayne Hawk. Wayne has written a number of technical articles on glass cutting and the nature of glass, and with his permission, I'm sharing his input with you below.
Yes, there is a phenomenom called "healing". If you
delay breaking out the scored glass for some time itis harder to break. The reason is theoretic, but here are two possible causes.....

-- 1. Picture (pun) the fissure as a very clean crack. At the bottom, where the crack disappears, it is being jammed back together by the compressive nature of glass surfaces. There may be a molecular re-attachment of glass molecules which makes the fissure less sharp
at the bottom, therefore, breaking is harder to start.

-- 2. Silicon-dioxide, major component of glass, can be dissolved in water, or moisture in the air. Such action is more likely at the clean bottom of the crack.

I prefer #1, but Encyclopedia Brittanica describes #2. The action of "healing" can be affected, either enhanced or retarded, by many factors such as moisture in the atmosphere, dry cut vs. lubricated score, elapsed time, etc.

Thanks Wayne -- I hope this helps everyone.


Y'all know my limitations where framing is concerned. I DO cut all the glass, though, and have noticed that it DOES 'heal' after a while. It seems Jim Miller pointed this out on an old thread.
When it 'heals', it tends to break jagged, leaving little chips and slivers along the cut.

Many thanks for your response and given my scientific background it makes sense to me now, it is just something I have not experienced, though I do recall something about the age of glass making it more difficult to cut.


Sorry for my very abrupt response to your post it was uncalled for me to be as harsh as I was.

I guess if I can offer any excuse is that when I saw the topic on the CPF sample paper and on this thread I got a bit worried that if all the questions for the CPF were so theoretical that the relevance of the exam would have very little meaning.

Reality is that I score my glass and snap it, I have never left it lying around to test this theory of healing, I will now even though the exercise will only be academic for me.

Thanks all, as I say I learn something new every day.

Originally posted by Dermot Cox-Kearns:
.....Reality is that I score my glass and snap it, I have never left it lying around to test this theory of healing, I will now even though the exercise will only be academic for me.
You've got it Dermot. Few of us leave our glass sitting around for days before breaking, which is probably how long the "healing" process might take. Years ago, I recall some framers saying, "Hurry now! Break that glass, before it heals....... :eek: " When you first heard that concern, it was a bit like an "Urban Legend".

Excuse me if I missed this but, I put a broom handle under the score an break the mirror for 1/4 plate.

Up until a few years ago, I had a diamond-tipped glass cutter that did a swell job on glass of any thickness with very little pressure needed. Some moron who worked at my shop dropped it onto a concrete floor, chipping the tip and ruining it.
Does anyone here know of a manufacturer that still makes these things, or does someone have one that they would be willing to part with?
My understanding (and please don't attempt to change it as I'm happily set in my ways) is that glass is technically a liquid. Healing of a score makes intuitive sense, if that's the case, without having to understand the exact mechanism.

I have had to replace some panes of glass in a very old apartment building and discovered that the panes had become thicker on the bottom than the top. Sort of explains why old windows start rattling (especially when you consider the interaction with wood which might not have been completely dry).

Just don't try drinking both the glass AND the whiskey, is my recommendation.
Lion Picture Framing Supplies, Birmingham England have the Shaw D-930 Diamond Cutter in their catalogue product code 2629 at UK£24.85.

I would say that either the Fletcher or TOYO oil filled Tungsten tipped glass cutters will give as good a result as a diamond tipped cutter.


Liquid glass……… you are right I had forgotten my science.
Apology accepted Dermot!
I've been cutting glass by hand for 32 years. Learned from my old granddad who was a glass cutter in Pittsburgh for PPG. My first memories were of him dropping a huge sheet on a green felt table and cutting many window panes out of it. I was fascinated then and still am with the feel of cutting glass. A mostly religious experience.
Trust me it does "heal"
Tip: Put a strip or two of masking tape on the underside of squares and straight edges to stop them slipping.Better than sandpaper as it wont scratch the glass.
Originally posted by Bogframe:
Up until a few years ago, I had a diamond-tipped glass cutter that did a swell job on glass of any thickness with very little pressure needed. Some moron who worked at my shop dropped it onto a concrete floor, chipping the tip and ruining it.
Does anyone here know of a manufacturer that still makes these things, or does someone have one that they would be willing to part with?
There are heaps of oil filled cutters on the market, only a few seem worth the extra $.
Get yourself one of these . . .

Bohle cutters

** Tried to get direct page link, but it takes you back to main page **

CLICK > (under glass processing) Glass cutting - Glass breaking (seriously, that's what is says !)
> Oil Glass cutters
> page 3, scroll down a bit to . . .

The SILBERSCHNITT 4000 Oil Glass Cutter, available in plastic handle (best balance and non fatigue for cutting 2mm to 6mm, IMHO).

My beloved Keiwa had fallen apart, now carefully patched up and still the best cutter I've EVER had (15yrs old now). I recently went looking for a backup, for the day it finally dies, and the Bohle Silberschnitt 4000 was nearest in quality of cut that I've found.

I also bought one at the same time for a framer client here, and when I saw him the other night, he said he loves it.
Toyo are absolute rubbish now, in my recent experience with trials. They used to be a reasonable cutter.

Oil will help keep the cut open, that's why they make oil filled cutters, but a dip in 3-in-1 oil pad will also do just as well prior to cutting.
Liquid glass, ahhh yes, it is a super cooled liquid, but check on the concept of it moving with time

We call it a cut gone cold over here, if left for too long after scoring, and it is noticably harder to break any glass when the cut is cold.

There's a few methods for breaking 6mm (1/4'') glass, and it really depends on the offcut size.
(Thicker glass is another animal.)
As mentioned by others, mirror is just glass with silver nitrate coating and backing paint (prepared and applied in a specific way of course), and is scored on the outer face.
FWIW . . .
If you've got a metre (bit over 3' or so) of offcut, you can pull the glass across the end of the bench until the score is 3" or so still on the bench, lift the glass 6" or so, and drop the glass downwards, snapping at the score. This is relatively easier than it sounds, and is a generally common industry method. The offcut is then slid vertically back and upwards on the leading edge of the bench, and removed to storage, and the remaining is cut the other dimension as required.

If the offcut is say just a foot or two, then lifting the glass at one edge (the score comes into) a little, place a texta / thick pencil type item under the score, and put pressure on either side of the score (slightly more on the smaller side) to run the cut.

If the offcut is less that an inch, you need to run with glass pliers, made for the thickness glass being cut.
You can have your local glass merchant CTS for you ! :D
Bohle Silberschnitt 4000
I think I'd try ANYTHING called Bohle Silberschnitt 4000. This is clearly not some wimpy, gold-tipped glass cutter from Home Depot!

Sounds like something you'd use to penetrate mountain bunkers in Afghanistan.

BTW, I got real excited about seeing a post from po'framer after a long absence, until I realized the post is almost three years old.
I was told once that glass was classified as neither a solid or a liquid, even though it certainly feel like a solid. The molecular nature of glass causes the scoring to start healing within a few minutes, the molecules want to join back together.

The longer the wait, the more resistance to breaking along the scoring line, and the more likely that you will get a rough break, or worse. That's about all I have to say about that.
This actually works.. I didn't believe it when someone told me:

Score the glass on your wall sizer.. then take it to a nice level table

put the tip of a pencil under where you started the score.. and i mean just the very tip.. then put pressure on both sides of the mirror.. you can lean on it into the table.... poof.. it makes a pretty nice little cut.. definately good enough if you are framing the mirror!!