# Grinding Holes in Glass Tops



## I'mNew2Frogs! (Jan 23, 2019)

So I want to grind (drill) two 2-1/2-inch holes in a glass top for some vents.

I see the bits at Home Depot/Lowes, seen some videos. Angle the bit, not too fast, continuous water flow over the work area.

Is it as easy as it looks or should I have it professionally done? I don't want to go through half a dozen pieces of glass trying to get the holes


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## andrewdingemans (Jan 15, 2019)

you have the process right. I find a running source of water is the best, but if doing indoors, use some clay or the plastic dam that comes with some drill kits to keep the bit submerged in water while drilling. depending on how thick the glass is, you can sometimes get away with a little bit more pressure to speed it up a bit, but not really needed. place a towel below the hole to catch the piece of glass you are drilling out. I find putting wood behind the hole doesn't prevent chips but prevents you from jerking forward as the bit gets all the way through the hole. going slower as you get to the end will help to lessen the blow-out on the other side. Use medium speed as slow will take too long, and fast builds up heat too quickly (unless using the garden hose to constantly feed cold water)

I think I have done about 100 holes in the last 10 years or so and have never cracked a tank once. I use the cheap ebay bits and so far get about 10-15 holes per bit, but the bits cut substantially faster if you replace them after about 5 holes.


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## JimM (Oct 2, 2018)

Easy peasy.
I used a drill press and plumbers putty to hold the water.
The drill press helps, and I highly recommend it if you have one available.

You can watch the depth gauge to monitor your speed.
You can actually go through surprisingly fast.

If not using a press you you're better off erring toward slower than faster, and cutting a wood guide to get your hole started.

...and yes get a decent bit. Don't guy that cheap crap from WalMart online that you see people using in videos.


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## bsr8129 (Sep 23, 2010)

super easy, i use cheap ebay bits, not sure how many holes out of them but plenty 20-30, maybe more. you dont need putty around the hole put some water where you are drilling and start to drill, then add more water either spray or pour from a water bottle onto the bit. 

2 inch hole shouldnt take more then a couple minutes at most. if you are spending 5 min a hole speed up your drill. 

i can do misting holes in under a minute.


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## Socratic Monologue (Apr 7, 2018)

Pretty easy, and worth learning.

Rumor has it that thinner glass is much more likely to break, so the thin stuff at Home Depot might be a challenge. I've drilled 3/16 and 1/4"

I like the putty dam to keep the water in. I like to take my time on each hole, ~5-10 min; I'd rather spend my time drilling than driving to get more glass.

I also like this bit guide:

https://smile.amazon.com/gp/product/B00V3UONCW/ref=oh_aui_search_asin_title?ie=UTF8&psc=1

I've only cracked glass that, to my surprise, turned out to have been tempered...


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## PhylloBro (Sep 21, 2018)

the bits at home depot/lowes are waaaay more expensive than on Amazon or ebay. You would pay more for the bit than probably multiple pieces of the glass you are working with. I use clay and make a little puddle around where i am drilling so much easier to work with than running water. it serves the same purpose just as well.


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## JimM (Oct 2, 2018)

Taking time is definitely much better than rushing and breaking.

I got a little cocky after my first hole, and did the next 2 (1/4" glass) in 30 seconds each or so. The drill press made this easy but I'd definitely have gone MUCH slower if holding the drill by hand.


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## rjs5134 (Feb 1, 2017)

You've already got plenty of good info but I used bits from Amazon and bits from HD. I use a 1" piece of rigid foam and drill a hole thru it 1st. I put the foam where I want the hole in the glass, press down and fill the hole in the foam with water. I use my cordless drill and adjust the speed continuously to not allow a loud screeching sound. I periodically lift the foam to check the depth and change the water. I also put duct tape on the inside to reduce blowouts and stop the glass from dropping to the bottom. If your patient it is worth the trouble and pretty easy.


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## I'mNew2Frogs! (Jan 23, 2019)

JimM said:


> Easy peasy.
> 
> The drill press helps, and I highly recommend it if you have one available.


Oh! Great suggestion, we have one at work I can borrow!!


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## I'mNew2Frogs! (Jan 23, 2019)

Thank you EVERYBODY!!!


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## I'mNew2Frogs! (Jan 23, 2019)

So window glass from Lowe's (or similar hardware store) is about 3/32 thick. Will this take the "shock" or the surge of a mist king nozzle when it first fires up? Is there a surge?


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## PhylloBro (Sep 21, 2018)

Thats really thin but there isnt any kind of "surge" or even a rattle from the mist king nozzles from what i can tell. The pump buzzes a little but thats it. If you arent sure you can maybe test it on a piece of glass if it is 3/32 and you can pick it up in store im sure it is not expensive. I would look for 3/16 at least though. Is there no petstores near you selling old fish tanks? Craigslist? Offerup?


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## I'mNew2Frogs! (Jan 23, 2019)

PhylloBro said:


> Thats really thin but there isnt any kind of "surge" or even a rattle from the mist king nozzles from what i can tell. The pump buzzes a little but thats it. If you arent sure you can maybe test it on a piece of glass if it is 3/32 and you can pick it up in store im sure it is not expensive. I would look for 3/16 at least though. Is there no petstores near you selling old fish tanks? Craigslist? Offerup?


I agree, 3/32 seems a bit thin!

I had not thought of used fish tanks. That's actually a GREAT idea! Thank you!


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## Encyclia (Aug 23, 2013)

Not sure if it's been mentioned here, but I use antifreeze in a clay dam (as andrewdingemans said). It seems to smooth things out and makes it so you don't have to use running water. I do almost all of my drilling inside or in the garage, so running water would be a big hassle. I have only broken one thin piece of glass (probably too close to the edge) out of probably 50 holes. It is a really useful skill to develop. As said above, go slow. Don't push, just let the weight of the drill do the pushing. Start at an angle until you get a "bite" then slow rotate the drill up to vertical over the hole. It really is easy and even the cheapest Ebay bits have served me just fine.

Mark


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## I'mNew2Frogs! (Jan 23, 2019)

I have access to a drill press, should make it even easier


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## Encyclia (Aug 23, 2013)

I'mNew2Frogs! said:


> I have access to a drill press, should make it even easier


Yes, probably, just make sure you don't put too much pressure on the glass. Go super slow, til you get the hang of it.

Mark


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## JimM (Oct 2, 2018)

Yep, use the depth gauge so you can eyeball your progress..also use your ears.
You can hear the tool bite.

Again better to er on the side of going slower.
If you were doing a bunch then after a few you'd be popping them out very quickly. For a project like this and not having done it before, just take your time.


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## I'mNew2Frogs! (Jan 23, 2019)

OK - I've got glass, the proper drill bits, plumbers putty to form my pool of water (or cutting oil).

Now, is there a rough calculation or rule of thumb as to how close to the edge of a piece of glass I can cut a hole?

5/8" dia hole

2-1/2" dia holes


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## PhylloBro (Sep 21, 2018)

I'mNew2Frogs! said:


> OK - I've got glass, the proper drill bits, plumbers putty to form my pool of water (or cutting oil).
> 
> Now, is there a rough calculation or rule of thumb as to how close to the edge of a piece of glass I can cut a hole?
> 
> ...


If you really think about the process itself, the distance to the edge has zero factor on the hole. You are drilling into the glass it isnt expanding or stretching. Therefore, there is no additional stress being applied to the edge. So as long as you do not accidentally knock the edge really hard (depending on thickness) right where the holes are you will be fine. The edge would only be an issue if the glass was reallyy thin. But even if you are drilling in the thinnest glass on the most narrow edge, the drilling itself has no effect if you are doing it right. That might be an exaggeration but my point is you should not worry too much about it being near the edge. lol


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## I'mNew2Frogs! (Jan 23, 2019)

PhylloBro said:


> If you really think about the process itself, the distance to the edge has zero factor on the hole. You are drilling into the glass it isnt expanding or stretching. Therefore, there is no additional stress being applied to the edge. So as long as you do not accidentally knock the edge really hard (depending on thickness) right where the holes are you will be fine.


This actually makes sense 



PhylloBro said:


> The edge would only be an issue if the glass was reallyy thin.


I'm working with 1/4-inch thick glass. Thicker than I wanted but we have two glass cutting shops (custom showers, curved glass, etc.) in our industrial park. I've been dumpster diving for a nice scrap piece. One of the guys came out asked what I was doing, told him what I was after and I was invited into the shop area. The owner cut me a nice piece of 1/4-inch (they didn't have 1/8 or 3/16). FOR FREE!!!


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## Socratic Monologue (Apr 7, 2018)

I've read a bunch of rules-of-thumb on distance from the edge. 

Here, I've read 3/4", 1", or not closer to the edge than the diameter of the hole. Reef sites I've read no closer than 1.5 times the diameter of the hole. 

If you buy glass drilled, many won't drill closer to the edge than 2x the thickness of the glass, but this is pros using a drill press.

The putty dam (the method I use) will limit how close you can get, since the dam has to have a minimum thickness. I've been using a saw guide lately, too, which needs a few inches from the edge to fit.


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## I'mNew2Frogs! (Jan 23, 2019)

Socratic Monologue said:


> I've read a bunch of rules-of-thumb on distance from the edge.
> 
> Here, I've read 3/4", 1", or not closer to the edge than the diameter of the hole. Reef sites I've read no closer than 1.5 times the diameter of the hole.
> 
> ...


Thanks,

I do have access to a drill press and I won't be in any hurry  I also bought plumbers putty last weekend, probably on a recommendation from you, getting ready for this project.

I don't need to get super close to an edge, especially with the 2-1/2" dia holes for vents. The 5/8" dia hole, I do want pretty close to the front of the glass for a Mist King nozzle. The closer I can get it to the front edge, I figure the better the coverage.

If I screw it up, I have an endless supply of glass LOL. I will have used up the freebie nicely squared up for me but there is always glass in the dumpsters.

BTW - When the owner of the glass place gave me the one piece, I got a nice quickie lesson on cutting glass and thick glass


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## I'mNew2Frogs! (Jan 23, 2019)

Thanks for everybody's help, looks like it was a success. A little rough around the edges, nothing a Dremel can't take care of. Not too bad for my first attempt. I'm just very happy I didn't break the glass.


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## Socratic Monologue (Apr 7, 2018)

Nice work!

I usually touch up the edges with regular sandpaper wrapped around a block or dowel (depending on the shape of the edge), though a Dremel would likely do the same, faster.


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## PhylloBro (Sep 21, 2018)

I'mNew2Frogs! said:


> Thanks for everybody's help, looks like it was a success. A little rough around the edges, nothing a Dremel can't take care of. Not too bad for my first attempt. I'm just very happy I didn't break the glass.


So happy for you for taking the big leap ! We knew you could do it and it came out perfect. If you want to buff the inside, wrap some sandpaper around something like a tube that will fit inside the hole and just pull it in and out of the hole while rubbing the inside edge it will protect your hand and smooth the edge. Congrats again ! It will only get easier now.


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## davecalk (Dec 17, 2008)

I'mNew2Frogs! said:


> Thanks for everybody's help, looks like it was a success. A little rough around the edges, nothing a Dremel can't take care of. Not too bad for my first attempt. I'm just very happy I didn't break the glass.


Excellent. Good job.


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## davecalk (Dec 17, 2008)

Encyclia said:


> Not sure if it's been mentioned here, but I use antifreeze in a clay dam (as andrewdingemans said). It seems to smooth things out and makes it so you don't have to use running water. I do almost all of my drilling inside or in the garage, so running water would be a big hassle. I have only broken one thin piece of glass (probably too close to the edge) out of probably 50 holes. It is a really useful skill to develop. As said above, go slow. Don't push, just let the weight of the drill do the pushing. Start at an angle until you get a "bite" then slow rotate the drill up to vertical over the hole. It really is easy and even the cheapest Ebay bits have served me just fine.
> 
> Mark


The plumbers putty is a great suggestion. So is the suggestion to angle the bit into the glass. As far as using antifreeze, if you use that make sure you clean the glass really well as it is very toxic. Personally I wouldn't use antifreeze. I don't use running water. I use a plumbers putty dam with water and crushed ice. 

Using plumbers putty, water, and ice, I have drilled many granite countertops, lots of tile and a whole lot of glass over the years.

The purpose of the liquid is to provide lubrication and thermal transfer. The ice is to help keep both the glass and bit cool. The water and ice together, along with slow and light pressure drilling, keeps both the glass and bit cool which is majorly important as heat and pressure are the major causes of breakage when drilling glass. 

Keeping the bit cool also helps keep the Diamond chips from fracturing off of the bit, due to thermal shock. Keeping the diamonds on the bit means being able to drill many more holes with that bit thus lowering the cost of the holes you drill.

One important note:
As your cut reaches the bottom of the glass, slowly take the weight of the drill off the glass. This slows the cut and lowers the pressure on the bottom sides of the glass which allows the bit to actually cut the last bit of glass rather then the bit popping the bottom out of the weakened glass. Ragged cuts on the bottom are caused by the bit shattering the edge around the last portion of uncut glass. Thus the reduction of weight at the end of the cut will give you a much smoother edge on the bottom side of the glass. 

Also taking the weight off of the glass at the bottom of the cut will allow you to make closer cuts to the edge of the glass without cracking the glass. 

For the smoothest cut, put a sacrificial piece of glass under the piece being drilled.

Personally I also like to put something underneath the hole to catch the water and glass chip slurry. Usually newspaper and a bowl, but not totally important. The mess is just easier to clean up that way.

Bonus tip. 
If you ever want to drill the side of a tank which is already set up, (ie. you don't need to brake down the tank.), you can use shaving cream rather than water as a coolant. Shaving cream will stick to the side of the tank and still give you cooling and lubrication. Make sure the glass is not tempered glass. Also make sure you lower the water level below your proposed hole cut, picture the little boy plugging the hole in the dike.  I tape around and a couple of inches away from the cut and / or will put cardboard below your hole to help contain any mess. Then put a 2 inch wide dollop of shaving cream where you will be drilling, and start slowly drill the glass. Slightly running the bit into and out of the hole will help keep the bit / glass cool and lubricated with the shaving cream.

Doing this is much simpler than having to break down the entire tank for one forgotten drain hole. No more having to siphon water out of the tank for years on end with a turkey baster or siphon tube. Been there done that.


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## Socratic Monologue (Apr 7, 2018)

davecalk said:


> Bonus tip.
> If you ever want to drill the side of a tank which is already set up, (ie. you don't need to brake down the tank.), you can use shaving cream rather than water as a coolant. Shaving cream will stick to the side of the tank and still give you cooling and lubrication. Make sure the glass is not tempered glass. Also make sure you lower the water level below your proposed hole cut, picture the little boy plugging the hole in the dike.  I tape around and a couple of inches away from the cut and / or will put cardboard below your hole to help contain any mess. Then put a 2 inch wide dollop of shaving cream where you will be drilling, and start slowly drill the glass. Slightly running the bit into and out of the hole will help keep the bit / glass cool and lubricated with the shaving cream.
> 
> Doing this is much simpler than having to break down the entire tank for one forgotten drain hole. No more having to siphon water out of the tank for years on end with a turkey baster or siphon tube. Been there done that.


This is a great tip that I'd not known before. 

Once the hole is drilled, is there a way to get a bulkhead (or something else to seal the hole around a drain line) in place?


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## davecalk (Dec 17, 2008)

Socratic Monologue said:


> This is a great tip that I'd not known before.
> 
> Once the hole is drilled, is there a way to get a bulkhead (or something else to seal the hole around a drain line) in place?


You do have to clear out the area around the hole inside of the tank.

There are lots of things you could do.


I probably would install something like this, a 1/2 Inch Slip x Thread PVC Bulkhead Fitting 










Then I would install a 90 degree shut off valve on the outside of the tank so I could shut it off if I needed to. To the valve I would install a barbed fitting so I could put a flexible hose down to a drain or 5 gallon bucket.

If you didn't want or need a shut off you could install something like this.










This is a Lifegard Aquatics 1/2-Inch Bulkhead Fitting Kit.


Do a web search on bulkhead fittings.

All kinds of things you could do.

Get your bulkhead fitting figured out before you drill your hole, because you need to size the hole according to the bulk head you have. 

It is a good idea to have all of your parts on hand before you drill the hole.


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## davecalk (Dec 17, 2008)

PhylloBro said:


> If you really think about the process itself, the distance to the edge has zero factor on the hole. You are drilling into the glass it isnt expanding or stretching. Therefore, there is no additional stress being applied to the edge. So as long as you do not accidentally knock the edge really hard (depending on thickness) right where the holes are you will be fine. The edge would only be an issue if the glass was reallyy thin. But even if you are drilling in the thinnest glass on the most narrow edge, the drilling itself has no effect if you are doing it right. That might be an exaggeration but my point is you should not worry too much about it being near the edge. lol


LOL is right.

Sorry, but a couple of your statements are not accurate. "The distance to the edge has zero factor on the hole" and "there is no additional stress being applied to the edge." These are not anywhere near accurate. Hope I don't come off grumpy, as it is late. Yes the things you said can be true, but "only IF one is doing it right."

But most people, as they are learning, rarely do it right as they start driling their first holes. This becomes especially evident when they are drilling holes near the edge. What people don't realize is that glass is fairly forgiving especially when one is drilling away from the edge. But the shattered / fractured bottoms that most experience as they are learning to drill glass is tribute to the stress that happens when folks are not "doing it right." Hence all of the correct advice that others shared about how to deal with the chipped out edges.

The things I shared about glass and bit temperature and about bit pressure are only some of the issues involved in drilling glass, but they are the most important issues. 

Glass thickness, distance from the edge, drill speed, drill pressure, consistency of one's drilling angle, the size of the glass, the size of the bit, the age of the bit, the amount and temperature of the water, and properly clearing the slurry, all of these are factors in drilling glass properly. 


I do agree with the point I think you were trying to share. People do worry and think that drilling glass is a mysterious art which is difficult to master. It is not. Drilling glass and cutting glass are pretty easy skills to master because glass is very forgiving. A person can make a lot of mistakes and still get a usable hole. 

And getting good at it is what practice is all about. 

Sorry if I stepped on your toes.


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## Encyclia (Aug 23, 2013)

davecalk said:


> The plumbers putty is a great suggestion. So is the suggestion to angle the bit into the glass. As far as using antifreeze, if you use that make sure you clean the glass really well as it is very toxic. Personally I wouldn't use antifreeze. I don't use running water. I use a plumbers putty dam with water and crushed ice.
> 
> Using plumbers putty, water, and ice, I have drilled many granite countertops, lots of tile and a whole lot of glass over the years.
> 
> ...


It's great that there is more than one way to skin a cat! I am very confident in my ability to clean an empty tank of any residue of antifreeze. I don't even let it get near the silicone, so all I have to worry about is glass. I don't think I would use it if the tank wasn't completely bare, though.

On the other hand, I would never have been brave enough to bring ice water up against glass that I am going to be applying stress and vibration to. I like that it would be possible to use your method inside (as opposed to having to use constantly running water in the yard). Maybe I will give it a try someday 

Mark


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## Socratic Monologue (Apr 7, 2018)

Thanks for all this. 

My concern was that if I drill a drain in an already-set-up viv, I'd be drilling that hole beneath the substrate somewhere, preferably as low as possible for complete-ish drainage. Getting a fitting inside the viv under the substrate was the complication I was trying to simplify. 

I suppose in a viv with one or another of the 'false bottom' media, a person could just dig out around the drain area. I use 'egg crate' on PVC risers, and so wouldn't be able to get a bulkhead fitting underneath. I was hoping there was some sort of solution to this that I wasn't aware of (some sort of rubber grommet, maybe).

I've set up all my vivs to be pumped out from above with an Aqualifter pump, which works, but is somewhat time consuming (since I have to supervise the process). Sometimes I regret this, but am not willing to tear them down to remedy it.



davecalk said:


> You do have to clear out the area around the hole inside of the tank.
> 
> There are lots of things you could do.
> 
> ...


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## davecalk (Dec 17, 2008)

Socratic Monologue said:


> Thanks for all this.
> 
> My concern was that if I drill a drain in an already-set-up viv, I'd be drilling that hole beneath the substrate somewhere, preferably as low as possible for complete-ish drainage. Getting a fitting inside the viv under the substrate was the complication I was trying to simplify.
> 
> ...


Actually there are multiple ways of doing this.


Cutting the egg crate.

This is probably the least expensive and easiest. Cut the egg crate back to where you can get your hand into the opening. You could use a wire cutter or multi-tool oscillating saw to make the cuts. This would allow you to use a normal bulkhead. Then you cut a larger piece of egg create and place it over the hole. Use zip ties to bond the egg create to the lower piece to cover the hole. The small rise in the ground actually makes the ground look more like actual ground because in nature the back wall / hill never comes down and does a 90 degree turn onto a totally flat piece of ground. 


Using string.

Drill your hole and then poke a piece of string through the hole. Then cut a small hole in the egg crate only large enough to get the nut through. With a grabbing tool, a stick with duct tape on it, what ever, reach down and pull the string up.Then run the string through the nut and and bulkhead, slide the nut down through the crack insert the bulkhead and use the string to guide the two together. 


Using a Blind Bulkhead

Lastly there are blind bulkheads that do exactly what you are looking for. They are not cheap and you do have to be careful to not blow out the back side of the glass, but they do work well.



















Here is a link to one Blind Bulkhead manufacturer. Bulkhead Blind Tank Fitting


This video shows how they are installed.


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## davecalk (Dec 17, 2008)

davecalk said:


> Actually there are multiple ways of doing this.
> 
> 
> Cutting the egg crate.
> ...


Just to be clear, the fear of blowing out the back side has noting to do with the bulkhead. But if you blow out the back side badly, it might not seal properly.

Also I probably would not drill this type of bulk head very near the edge. I don't speak from experience, but I'm guessing that as it is tightened there might be the possibility of putting irregular pressure on the glass which could crack the glass.


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