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Plaster lead mold QUESTION

post #1 of 35
Thread Starter 
I hear from several sources that plaster of paris makes a decent lead mold material.

Is there anything else that is needed to be done before using such mold?

Sprayed with sealant? Baked in an oven?

Mine are still too damp to pour lead into. The moisture makes the lead boil.

I'm going to try baking it in the oven for a while.

post #2 of 35
You're right. Plaster will work fine, but as in any mold material involving hot metal, you need to dry it out, as moisture in the mold will turn to steam as you pour molten metal into it, and steam bubbles will create voids in your castings. What are you trying to make? There are quite a number of aluminum Do-it mold available to cast various types of weights and jig heads, as well as a blank, if you want to create something custom.
post #3 of 35
I tried plaster, but basically a plaster mold works for one use only. I make my molds out of wood. For smiling bill jigs, I drill the mold; for most I shape the wood with a dremel tool. The wood lasts for about 10-15 castings. I can make 2 or 3 molds in less than 1/2 hour and can pour about 30 jigs with these molds. That is way more of any one size than I bother to make.
post #4 of 35
Thread Starter 
Figured it out.

I made my molds out of Hydraulic Cement, and let it set for an hour:

Then I baked it at 500 degrees for an hour to dry and cure it. The mold works GREAT!

I've made about 25 trolling sinkers and dimpled "Sting Silver" type jigging spoons.

I was not impressed with the plaster molds, but these are actually very nice. They make lures just as pretty as my Do It molds.

post #5 of 35
I use doit molds but still use plaster when I need to. I can get 25-50 lures out of one. It is important to let them dry thoroughly. Smoking them with a candle helps the castings separate. Dental plaster (ask your dentist) is a better quality. Try a search, I think this was discussed on the main forum in the past. Where can you get hydraulic cement? Home Depot? Do you vaseline the first half of the mold before pouring the second? How do you form the pour spout in the cement? Are you making just a single piece mold? thanks. pawlie

[This message has been edited by pawlie (edited 10-20-2002).]

[This message has been edited by pawlie (edited 10-20-2002).]
post #6 of 35
Good questions pawlie. Im also interested in making molds. Ive tried Bondo, the car patch material . My results were marginal at best. I let the Bondo dry for only 5 or 10 min. perhaps it wasn't long enough.I believe from what Ive heard, the RTV (room temperature valcanizing) products make very good molds and last for ever.The products are pricy and seem to be hard to work with,although I havent tried them. Like the cement idea its quick ,cheap and fast to make, the only draw back may be how well it duplicates the origional.Lets keep this dialogue going.Email if you like.
post #7 of 35
Thread Starter 
Sorry for the incomplete info.

After the bottom half (as pictured) sets up, in 15 mins or so, you pull out the sinker and lightly coat everything with Vaselene. Put the sinker back in, and pour more cement over it.

15 minutes later, you simply pull the mold apart. While the cement is relatively soft, you notch out a pouring channel, then re-assemble everything, and let it cure for an hour. Then put it in the oven at 450 degrees for an hour, and you are set!

A pair of 2" spring clamps makes for tight, perfect molded lures everytime.

I have a spinner-making kit to make the eyes with, but Capt Skip just gave me a great idea for "normal" people. Use copper wire. A couple of feet will make a LOT of lures!

I make the loop from stainless steel wire, and then bend the ends so they anchor in the lead.

Home Depot sells several types of quick-setting cements. You want the one WITHOUT sand. I use the namebrand "Rockite"
because it's in my shed.

You can also make your own. Mix Plaster of Paris and Portland Cement 50/50, and it works great.

the addition of the portland cement makes the molds MUCH more durable. As long as you don't drop them, they may last forever.

Hope this helps.


PS- I notch out the channels with a knife, if I catch it early enough, or with a Dremel tool if it gets too hard.


[This message has been edited by thill (edited 10-20-2002).]
post #8 of 35
This is probably a stupid question but how much water do you add? Make it soupy or thick?
post #9 of 35
You can also use a couple of nails to help you make sure the halves go together correctly. Sink the nails (head side down) in the first half while still wet. Vasoline on the nails like the rest of the mold. Roofing nails work well as they are short and have a large head.

I have tried a number of different things for making molds. Stuff like plaster is fine if you are only wanting to make a few items. I have yet to find a substance that will hold its shape, hold up for long, and consistanly produce the same size lure/weight. The only thing that has worked has been aluminum. Either blank do it molds or scrap pieces. Use a mill to carve them out. For some stuff, a dremal works fine. You can get some finishing stones at a place that sells milling supplies to finish the mold. These are similar to stones that you would use to sharpen a knife. You can shape them on a belt sander so they'll fit the mold better. My $0.02 worth

post #10 of 35
Thread Starter 

You want to add only enough water to make almost dry lumps. Mix for 2 full minutes after that.

Then put it into the mold, then vibrate the mold. The stuff will literally turn liquid before your eyes, and flatten out. It will stiffen back up when you stop vibrating it. Strange stuff.

Put your lures on top, and then vibrate until they sink half way, as you wish. Proceed from there.

Jig Man,

The addition of portland cement makes a FAR superior mold than plaster of paris.

I believe these molds will last a very long time. I've poured about 50 of them already, with no change.

post #11 of 35
Sounds good THill. Keep us updated on the molds. Always good to have other sources of mold making materials at hand. Sounds like the stuff is pretty easy to use too.

post #12 of 35
Thread Starter 
Definitely easy to use. Not as messy as the plaster, IMHO.

The first time I tried, I made it liquid, and that was a pain.
post #13 of 35
trill ;hi went you make the moles with plaster/paris add 25% of portland the mix. it willmake the mole a little hard. put 4 big marble one it each corner .
good luch

post #14 of 35
Thread Starter 
Hey... I just posted that on the other board!

U following me?
post #15 of 35
When you vibrate the mold, what do you mean??? Are you just shaking the mold, or something else?? I don't want to shake it and have the lure fall further down in this stuff. Is there some other way to do this, or is it just trial by error?? Any help would be appreciated. Thanks, Fozziebigbear
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