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StephEm

Advice - How to fit cork lids for canisters?

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I recently bought some natural cork lids that I would like to use for canisters. The cork lids are 4.5 inches in diameter on the top, and 4 inches on the bottom (http://www.corkstore.com/Products/Bark-Top-Stoppers/Rough-Natural-Top-Cork-Stopper-BT08-Bag4) and the canister might look something along the lines of this example: https://www.pinterest.ca/pin/47428602312927964/).

Since I'm not making a clay lid, how would I best determine how wide to throw the inner lip of my canister?  I will be glazing the interior of the canister as well.

Many thanks for any assistance in advance!

Edited by StephEm

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Figure out the shrinkage rate of your clay, most are around 12%.  And then multiply the opening size you want by 1.12.  that will be the setting you set your calipers to.  So if you have a 10 inch opening, and your clay shrinkage is 12%, make the opening 11.2 inches (10*1.12)

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StephEm-

i agree with liam’s calculations, but a quicker method is to just make the opening the size of the wider end. Since your cork is 4” at the bottom, multiplying that by 1.12 results in 4.48” which is probably close enough.

Regards,

Fred

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I use a method for objects which need to have a repeated specific diameter (openings on oil bottles specifically); I used an old dried up sharpie marker, and wrapped tape around it until it was the correct diameter for my opening (using the same calc method Liam suggested); now I just throw my necks a little more snug than they need to be, take my tool, and shove it in there while throwing. Bam, the neck is the exact same size. This might not work very well for something that is 4", but anything under 2" I think would be a great, repeatable way.

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Sorry, but the inner engineer in me compels me to point out that multiplying by 1.12 gives you an opening 12% bigger than the finished opening...  which is not the same as a finished opening that's 12% smaller than the original.

With 12% shrink, your finished opening is 88% of the original (100% - 12%).   If you make it 11.2", and it shrinks exactly 12% - your finished size will be 11.2 x .88 = 9.856.

Since 'Finished' = .88 x 'Make',  you would divide your desired finished size by .88 to arrive at the 'Make' size.  ('Make' = 'Finished' / .88.)  So... to arrive at a 10" finished size:  10" / .88 = 11.36"  (or, for a 4" opening to fit the corks in question:  4" / .88 = 4.54" )

Obviously, at theses sizes, the difference  is small enough that it's probably less than your margin of error in measuring - but if you're working on something a lot larger, it would become an issue.

 

 

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Rockhopper-

You are correct with the math, and in actuality that’s what I meant to say. Only excuses I have are as follows:

1) was waiting for a bus in 34 *F weather with no windbreak and a NW wind of 26 mph.

2) I was rushing, since I was typing on my phone and thus not wearing gloves. Face it, I just wanted to put my hands back in my pockets!

So yes, my algebra was incorrect, however I was really attempting to suggest a quicker, non-math or ruler method, which also avoids the variable shrinkage rates of different clay bodies, which are only accurate with consistent moisture content clays. People’s individual forming  techniques and how much water they use while performing those techniques  can have a huge impact upon the moisture content of a 12% shrinkage clay body (ie. if one throws with a lot of water, their shrinkage will be a lot different than if they throw dry), hence: “It depends” and your mileage may vary!

Thanks for the correction, Rockhopper!

Regards,

Fred

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Rockhopper has it spot on

I always have posted this on the wall this written out above my throwing wheels

I work this up with a shrinkage bar of all clay bodies I work with. Mark the bar in metric so the percentage is easy to see. Make the marks that sjow 10CMs

(you would divide your desired finished size by .88 to arrive at the 'Make' size)

There have been many a post on this subject-I posted photos og my bars about 3-5 years ago.

 

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4 minutes ago, Fred Sweet said:

Rockhopper-

You are correct with the math, and in actuality that’s what I meant to say. Only excuses I have are as follows:

1) was waiting for a bus in 34 *F weather with no windbreak and a NW wind of 26 mph.

2) I was rushing, since I was typing on my phone and thus not wearing gloves. Face it, I just wanted to put my hands back in my pockets!

So yes, my algebra was incorrect, however I was really attempting to suggest a quicker, non-math or ruler method, which also avoids the variable shrinkage rates of different clay bodies, which are only accurate with consistent moisture content clays. People’s individual forming  techniques and how much water they use while performing those techniques  can have a huge impact upon the moisture content of a 12% shrinkage clay body (ie. if one throws with a lot of water, their shrinkage will be a lot different than if they throw dry), hence: “It depends” and your mileage may vary!

Thanks for the correction, Rockhopper!

Regards,

Fred

Fred You got to move south to a warmer climate dude.

Over here on the coast (due east and north a tad from you)it rained 1 inch last night and is a balmy 59 degrees

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Mark-

I am south! And you know it, since you said: “...due east (actually you’re west of me) and north a tad....”

Just another day down here. It’s  a “Blue Norther”, where there’s nothing to stop the cold coming down from the Arctic Circle, except for barbed wire fences, which only do a reasonable job stopping cattle and other wildlife! It’s alright, give it a couple of days and we’ll be back in the high 60s -low 70s! You know ”pneumonia weather”!

Thanks for looking out for me, my friend Mark.

Best wishes,

Fred

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Glaze takes up a surprising amount of space in a hole, especially because cork tapers don't leave a lot of wiggle room. 1/16" makes a huge difference in how deep the cork sits. It would be smart to make a couple test pieces to be sure.

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for a while I was making jugs that were plugged with corks.  I finally settled on one cork and wrapped the cork with masking tape (the blue stuff) to create a tool to make the correct hole size.  Took several tries  to get the number of layers needed for my clay body, but the 'tool' works fine.  the 'tool' solved both the size of the hole and the angle of the taper right for the corks I wanted to use.  For larger corks the idea should also work.  

LT
 

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2 hours ago, Fred Sweet said:

Mark-

I am south! And you know it, since you said: “...due east (actually you’re west of me) and north a tad....”

Just another day down here. It’s  a “Blue Norther”, where there’s nothing to stop the cold coming down from the Arctic Circle, except for barbed wire fences, which only do a reasonable job stopping cattle and other wildlife! It’s alright, give it a couple of days and we’ll be back in the high 60s -low 70s! You know ”pneumonia weather”!

Thanks for looking out for me, my friend Mark.

Best wishes,

Fred

Fred I got that east /west  screwed  up as I was sitting on the couch with a cup of hot coffee in a bone chilling 70 degree dining room.

I shoulkd know better as my Brother published a book called East west back in the late 80s.I have a copy-its an art book only a small run made.

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I make rulers out of fresh clay (not leather hard) for every kind of clay I work with, marked in 1/4", six inches long. (Use an embossed plastic ruler, oiled up. The numbers will be backwards, but legible.)

After firing, rulers are used to measure desired finished width. Example: place the ruler at the 4" end of the cork, (number will be greater than 4" because the ruler has shrunk), then measure the wide end. Average the numbers to get the width to make your opening. 

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As someone with a lathe and a woodturning background, it is easiest to do the shrinkage calculations and then aim just a bit smaller.  It is much easier to slightly turn down the cork than to get the pot perfect. 

I just did this recently when making a replacement pot for someone who wanted to re-use their own cork. 

 

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I made a run of bottles a few years ago, and I built the bottles first and then ordered the corks. If I were to do it again and needed to be able to reproduce the jars in later batches, I'd take measurements so that I could set up a pointer and throw to a gauge. I agree with Jeff about getting them a bit bigger and sanding them down. Sometimes when you get a wide opening like that, you need to be really mindful of warping and having the room to adjust the cork would be a good thing. 

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