Short answer is to test them. Cast is usually quite brittle and will crack easily, wrought will bend and tear like wrought.
Phil

Easy way to tell if you have cast iron or something else.

Place the weight on 2 pieces of wood(2X scrap laid flat works fine) so that the ends are supported but the center open.
Put your eye protection on.
Take a moderate size hammer and hit the center unsupported area of the weight with enough force to intend to slightly bend it.
If you snap it into 2 or more pieces it`s cast.
If it bends it`s something else.

Unless you can use the cast iron weights for weighing down something, I would scrap them out and use the money to get something useful.

Having see numerous wrought iron weights, I have a theory about it. Goes like this: While casting was probably the cheapest way most of the time, there are circumstances where forging could make sense. You got a blacksmith shop and business is slow. Ya got a big mountain of scrap. You can take it to the scrap and get a penny a pound or you can turn it into something you can sell. Sash weights were a "commodity". So ya beat a pile of scrap into something that brings a little more than scrap price and you can buy a bag of groceries!

I'm with Dave, if they're round, cast iron, square, they're wrought iron.

That's my story, and I'm sticking to it.

I saw a guy who used window weights as a hold down on his anvil. He had a piece of chain attached to a weight loop and then to the anvil base. He would put the object to be worked on the anvil then drape the chain and weight over it and the anvil face. Not totally fixed into place but it will stop your work from flying off when its hit or not roll around when you trying to punch holes...

They will be sent to China and come back as an ASO at Harbor Freight. LOL

That's priceless!

We pulled a hundred or so out of our house (1890s) when we re-did the windows. I lined a path that gets particularly muddy with them. They make OK stepping stones :P

Bought about 100lbs of window weights earlier. What are their uses in forging? I intend to make one into some sort of rounding jig. They weigh about 5 lbs each. What can I use them for?

I hope you didn't pay much for them! They are cheap cast iron, well nigh worthless. Pretty much unforgeable. They work well as trotline weights and are otherwise pretty useless.

Alright, I live in a major cat-fishin town, I have a use for abnout 5 of them. I only paid scarp for them. If all else, I'll put em' on ebay

Depends, are they round or square? We run into a lot of square wrought iron ones around here. I've theorized they could have been made during the depression as a way to turn your scrap pile into a little more cash than the scrap yard would pay.

They're round and weight about 71/2 lbs apeice. Most of them are Christopher brand cast iron

good to know i have a square one i found last week while cleaning out a shed i will definitely be holding on to it now thanks Danvil

they make good clinker breakers for welded fire pots

The rounded end can be clamped in the vise and used as a stake. The shape can be altered by grinding and sanding.

We use them at the iron pour in Tucumcari to remelt in to other objects but as said they are a poor grade of cast iron, real poor.

I plan on making a stake out of atleast 2, I may donate them to the ag shop for some odd use. I'm gonna try to forge one, jus to try it

Waste of time and fuel, but you will know more after you try. The best use for them, is weight for Nakedanvil's flypress modification.
My Dad made gate closers with them.

I didn't even think of that! Or maybe make it the weight for my big tool box lid that has a problem with breaking fingers

The best use for them is............. Repairing an old wood sash window, I save them for when I remove a window to install new glass or other repair the cords that hold the weight are often rotted away and the weight falls down inside the wall cavity, they can be a pain to fish out easier to just install another one

Theres no sash windows in my house, nor any of my neighbors.

when you siad you paid scrap rate---was that scrap rate for cast iron or scrap rate for steel? Cast iron is usually much lower than steel (like 1/10!)

I paid scrap for steel, for $10 and finding another local maker I don't care if I got burned.

If you find anybody building a sailboat that is good ballast!

For $10 taking a chance was probably worth it. I spent that much on a bad table saw for its stand the other day.

Phil

Anyone have creative suggestions for old sash weights?