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Author: Subject: How much should a 200ml can of spray paint weigh?
John G

posted on 18/9/20 at 05:17 PM Reply With Quote
How much should a 200ml can of spray paint weigh?

A bit confused! I purchased two 200ml cans of spray for my sons bike. When they arrived they seemed a touch light. I weighed them in at 139g. I messaged the seller with the idea that 200ml should weigh 200g plus the weight of the can.
This was the reply.

New message from: pricesaver.126589 Top Rated Seller(2,925Red Star)
Hi,

Thanks for your message.
We are extremely sorry for the inconvenience caused to you.
No this is not the faulty batch, normally we consider 1 litre as 1 KG but in aerosol this is compressed and weight less than the ML.
The ML will work only when it will be sprayed that ML is count as produced material out of the spray can.
Its weight will be around 120 to 150 grams for 200ML.
Am I losing the plot? Have the laws of physics changed or do we measure spray cans in a different way?

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jps

posted on 18/9/20 at 05:34 PM Reply With Quote
200ml of water weighs 200g. 200ml of marshmallows does not.

I guess the same principle is at play here. Volume is one thing, weight another.

[Edited on 18/9/20 by jps]

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Slimy38

posted on 18/9/20 at 08:05 PM Reply With Quote
I'm not sure how the weight of something changes because it's compressed, if it's 200ml of paint it should weigh 200g (ish). Whether the tin only contains 200ml of paint, or 200ml of paint and 200ml of propellant, it should still weigh more than 200 grams.

But I had to go check. So I've just dug a tin of clearcoat out of the garage (the nearest unused tin of spray paint I had). A 500ml tin weighs 513g. I might expect that the can weighs more than 13g, but the weight of the tin in grams is still higher than the volume of the paint in ml.

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BenB

posted on 18/9/20 at 09:39 PM Reply With Quote
Hmmm. I suspect most people would expect "200ml" of spray paint to be 200ml of paint at atmospheric pressure. If they're talking under compression then the density will increase a little but not much as most fluids don't compress that much. When the paint gets squirted out the can you'll get a mix of paint and aerosol but if they're saying there's only 200ml of that then that's cheeky. On that basis it could be zero paint, 100% aerosol and still be "200ml". Then again it could be 200ml of paint and no aerosol!

Sounds like they're saying it's 200ml of atomised paint. Which mostly will be propellant.

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Steve126

posted on 18/9/20 at 09:53 PM Reply With Quote
I've just weighed a 150ml can of Hycote top coat and that only weighs 135g
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MikeRJ

posted on 18/9/20 at 10:31 PM Reply With Quote
quote:
Originally posted by Slimy38
Whether the tin only contains 200ml of paint, or 200ml of paint and 200ml of propellant, it should still weigh more than 200 grams.


This simply isn't true, it depends entirely on the density of the fluid and the weight of the tin. Water weighs about 1kg/litre, other liquids have different densities.

I've just weighted an unused 400ml paint aerosol and it came in at 320 grams and a good chunk of that will be the can itself.

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coyoteboy

posted on 18/9/20 at 11:22 PM Reply With Quote
Density of acetone is about 780g/l and the solvents are the bulk of the weight of paint. A tin is going to be what, 50g?

I've always wondered if I was being diddled but it's impossible to tell without wasting a tin.





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MikeR

posted on 19/9/20 at 08:29 AM Reply With Quote
I could sell you a 200ml tin of air. It would weigh the weight of the tin. If I had a thin of propellant and air, it would be the weight of the tin, propellant and air.

(I'd made the same assumption till I read this thread and it clicked)

I guess tins have a lot of propellant.

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Slimy38

posted on 19/9/20 at 10:25 AM Reply With Quote
quote:
Originally posted by MikeRJ
quote:
Originally posted by Slimy38
Whether the tin only contains 200ml of paint, or 200ml of paint and 200ml of propellant, it should still weigh more than 200 grams.


This simply isn't true, it depends entirely on the density of the fluid and the weight of the tin. Water weighs about 1kg/litre, other liquids have different densities.

I've just weighted an unused 400ml paint aerosol and it came in at 320 grams and a good chunk of that will be the can itself.


Yeah I'm not sure how I came to that initial conclusion... although it's interesting you have a tin of paint that is lighter than I would expect. Surely there would be at least some kind of consistency?

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Dingz

posted on 19/9/20 at 10:37 AM Reply With Quote
Just wieghed a new 500ml tin of halfords primer, it weighs 485g. an empty 300ml paint can wieghs 90g. It looks like it is volume of paint + propellant?





Phoned the local ramblers club today, but the bloke who answered just
went on and on.

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smart51

posted on 19/9/20 at 06:21 PM Reply With Quote
ISTR that a spray can is 10% paint. Cellulose paint has an equal proportion of thinners. I don't know about acrylic paint. The rest is propellant. The propellant gas doesn't weight much.

Acrylic has a density not far off 1. Thinners will have a density less than 1. So if an empty can is 90g as above, and the paint plus thinners is about 34g, 139g for a full can doesn't seem far off.

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