Measuring clay pot thickness - ideas please

Hi. Just thinking this through and wondering if it’s possible.

I’m mainly just wondering if there is a sensor on the market that will do this.

I do a bit of pottery and would like to have something to measure the wall thickness of items as they are being made. So basically it’s a hand-held sensor to measure the thickness of wet clay.

This would be used mainly when making forms with small openings - like bottles - where you can’t get your fingers in to measure the wall thickness by hand.

An experienced potter would not need this but I’m a beginner and it’s something I think I could use until I develop the sixth sense that most potters seem to have.

I have seen people do this with long plastic calipers but the results never seem very reliable as you are pressing two calliper tips, one almost unseen, against wet clay which provides very little resistance. The margin of error is probably greater then the measure.

So imagine you have a pottery wheel, stopped temporarily, with an item consisting of wet clay, access to the outer surface is straightforward but to the inner surface is very difficult, and you just want to know the wall thickness at several points.

I know there are many devices for measuring the thickness of drywall etc, so maybe the same technology in a more convenient form?

So any ideas?
Thanks

Welders in training learn to weld by breaking every weld.

Your fingers will learn to measure the thickness by feeling your other finger as you work. Cut your first 100 tries lengthwise to see variations as you move up the piece.

Ultrasonic thickness gauges are commonly used to measure thicknesses of many different materials. The sensor is placed on one side of the object to be measured. It sends out an ultrasonic pulse, which reflects off of the far surface. If the speed of propagation is known (as it is for many materials), the device can calculate the thickness using that speed and the time between sending the pulse and receiving the reflection.

Ultrasonic methods have also been tried in civil engineering to measure the compaction of clayey soils of varying moisture content.

So apparently ultrasonic waves can travel through clay.

You could buy a relatively inexpensive ultrasonic thickness gauge and give it a try. You'd have to do your own calibration. If you get reasonable results, after some experimentation you will probably learn whether you need to calibrate with each different clay mixture you use.

Here's an example:

https://www.amazon.com/HT-1200-Ultrasonic-Thickness-Measuring-2-2-225mm/dp/B07FL2FRNH

$100 is very inexpensive compared to models from reputable firms such as Defelsko. So this example may or may not be a POS.

The indicated range (2 to 300 mm) is for a particular material. Undoubtedly it is different for clay.

They make what are called 'air gauges' that use a low pressure stream of air. I saw some maybe 50 or years being used in a pottery plant. One I remember looked almost like a 'V' which he used to measure the wall thickness of a cylinder. See if this helps: https://willrich.com/wp-content/uploads/2014/11/Air-Gaging-Basics.pdf

My 3D printer has an induction distance sensor to autolevel the aluminium printer bed. It achieves a very accurate distance measurement.
If you could use a small metal object and hold that to the inside of the clay and then use the inductive sensor I think you would be able to measure the distance between metal object and sensor.

Yep, that’s what is what I was looking for. Induction proximity sensors. Didn’t know they existed but logic said they should. Loads of them on AlixExpress with many different characteristics. Cheap as chips. It’ll take a while to research them and evaluate them but I think there’s a good chance I’ll find one able to detect a small metal target object through 15mm of wet clay. Thanks for that hmeijdam. And thanks to the others who responded - all suggestions are useful and interesting.
Cheers

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