Hello, new member to the forum long time lurker.

So I been awfully curious as to how heavy a "bullet proof" curiass was compared to plate armor made before guns started dominating the battlefield. From what I heard, you would need at least 4mm of steel to have a hope of protecting you from a musket and I've heard claims that some historical curiasses could be as thick as 9mm.

I've been browsing some musuem sites that provided the weight of 3 quarter armor but they don't see to provide the armor's thickness. Would anyone happen to know how much a 9mm curiass would weigh and is there some some sort of mathematic formula you could use to determine a curiass based on its thickness?

Thanks in advance.

Cuirasses were only that thick across the chest. The thickness tapered off at the sides. It isn't possible to come up with a simple equation to determine the weight.

Here is a typical example. The breastplate is almost 9 mm across the chest but tapering down to around 6 mm at the shoulders and 3 mm at the sides. Weight is 7.5 kg (note that this isn't including a backplate).
http://www.allenantiques.com/A-209.html

Thanks for the anserw. That's a lot lighter than I'd thought it be.

I found a video of people shooting at a 5mm-7mm, I wonder if a 9mm breastplate would be able to withstand some of the more powerful shots it failed to deflect.

https://www.youtube.com/watch?v=aGj0M-NJDGA&ab_channel=SylviaLeever

There are at least three incidents of these breastplates stopping cannon balls.

Proof armour is a balance of more then just the metal's thickness or composition.

There the construction, its not uncommon for armours made of squares, scales or lamellar to have them pushed into the wearer's body.

The technical ability of time really matter, the entire Anima school of armour is born due to the problems with heat treating large plates to the newest stranded.
The later Duplex armours with the two layers of metal could easily have both a hard face an tough ductile layers.

The angle of the armour surface helps too, see the shift towards the pescod breastplate and its greater deflection angles.

Henry the VII's armours are a great look at how this change happened.
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I thought lamellar was good because the plates would fly away when shot, taking the bullet with them

Another issue that might be worth mentioning is that 9mm sounds unlikely for a one-piece breastplate. Sounds to me more like it'd be the combined thickness of the breastplate (which might be pretty thick already) plus a similarly thick plackart -- say, 5mm cuirass/4mm plackart or 3mm plackart on top of a 6mm cuirass. And as has been stated above, this would represent the maximum thickness on both items, probably right on the central ridge.

That level of localised thickness is maybe an artefact of the forging procure, if your starting with a billet you hammer it in to a blank an from there shape it from the centre stretching out the metal more towards the side an edges.

If you have a large even plate to work with you still have a greater thickness in the centre but its not nearly so thick.
Dish an raising breastplate from a 2-3mm thick plate doesn't give the same amount of metal movement.

If you look at modern helmets there often dished in to half's an welded, it makes then uniformly thick.
Heres one of the few cases of a helmet being dished from a billet, note that its stretch the metal alot
https://www.youtube.com/watch?v=JOztX_5uO9M VS
https://www.youtube.com/watch?v=0_lsij2Qa50 the modern welded halfs.


Makeing armour thicker was the easiest way to make it stronger against shot, more metal was by the time armour thickness start to rise, a really cheap to solve the issue.


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Besides making something weightier has long been away to give the idea of quality.