As an avid scuba diver, I often have the opportunity to travel to remote places for work and sometimes I will take my dive gear for a quick dip in the water. It’s also a chance to go spearfishing.
On one occasion after getting suited up I realized that my lead weight dive belt was missing. I guess I had left it somewhere on the beach a while back.
Not wanting to miss out on the trip I just filled my BCD jacket with a few rocks and down I went. It was a great dive but I did spend the first 10 minutes trying to work out how many rocks I needed for my buoyancy.
Upon arriving home I had a thought about how to make some scuba weights. I had made some fishing sinkers in the past so it couldn’t be that hard.
How to make scuba weights using a concrete mold
I started by making the concrete mold out of 4 parts sand and 1 part cement. You could use plaster of Parris but I wanted a mold that was strong enough to make 20 diving weights or more. Who knows I may even be able to sell some to the dive shops and start a new business.
Once the mixture is the consistency of playdough coat your existing dive weight in glad wrap also known as cling wrap. This will stop the cement from bonding to the lead weight.
Push the original lead dive weight into the mold with any writing or numbers facing down into the mold this is the same way the original one was made. Leave it in the mold for a few hours until it starts to set and then you can remove it.
Now we need to wait a week or two so the cement sets fully and dries out. We can then bake it in the oven at 110 deg C (230F) for a few hours to fully drive out any moisture. Congratulation you have just made a concrete dive belt lead mold.
Using a ready-made Trident Poured Lead Mold
The great thing about these ready-made cast lead diving molds is that you can set the size of the scuba weight just by how much lead you pour in. The marks around the edges can help you work out each size be it 1 to 10 pounds. As always preheat the casting mold before you pour in the molten lead to prevent any stress cracks.
These will give you a better finish than a concrete mold but I wanted to prove the concept that I could make diving weights just with the products I had on hand.
Where to get free lead?
One way which is a lot of hard work is while you are out scuba diving around jetties and pylons is to keep your eye open for lead sinkers. Put them in your dive bag. This way you are also cleaning up the ocean floor.
Another way is to use car batteries. I had two old car batteries and some old lead roof flashing lying around the house that I could use. But I still needed more lead so I went to a few car battery workshops and asked if they had some old ones in a bin. Most were more than happy to give me a few. Some already had deals where they were selling the batteries to extract the lead.
This way was able to grab another 5 car batteries. The good thing was these car batteries had already been drained of battery acid. Which made them safe to open up but I did quickly fill the deep cycle batteries up with water to dilute any remaining acid.
The next step was to open them up and extract the lead plates.
How to remove lead from car batteries.
This is where you have to get down and dirty. Don’t be afraid to get rough and smash the outer plastic casings up. I use a large ax and a smaller tomahawk to split the batteries open.
Be safe and use saftey gear like gloves, eye goggles, long sleaved overalls, and a face shield.
This is a messy process and that’s why I like to make sure there is no battery acid anywhere, as bits of plastic will fly everywhere. Once you have extracted all of the lead its time to pack up all the rubbish and wash the lead to get rid of any dirt, and grass that may be on the lead.
Be sure to dry the lead 100% before you place them in a pot for melting. Any trapped water can cause an explosion in the hot liquid lead if its wet.
This is a hazardous process that must be done outside in a well-ventilated area and using an air respirator, eyeglasses, face shield, leather gloves, boots, and long cotton clothing. Melting lead is very dangerous as its hot liquid metal and toxic.
Lead melts at 327.5 °C (621.5 °F) so if the liquid metal touches any part of your skin it will instantly burn you. Please take care.
I like to use a portable camping stove to heat up an old iron pot. It will take around 10 minutes depending on how hot your flame is to start melting the lead pieces.
Its good to have a long metal spoon or a set on tongs to constantly scrape off any impurities that may float to the surface of the liquid lead. Once all of the lead is melted and you have scraped off all of the junk off the top you will be left with a shiny silver liquid. We are now ready to pour into our molds.
If you don’t have access to an outside gas stove you could always stoke up a fire pit and melt your lead that way. If you are in a remote location check out our post on how to start a fire without matches using high tech gadgets.
Pouring liquid lead into molds
I like to preheat the concrete mold to around 150 deg C for 1/2 hour beforehand just to make sure there are no water molecules in the cement which could have been absorbed over time. Coat the inside of the mold with talcum powder. This tends to make it easy to remove the cooled lead weight out of the cement mold.
Remove the iron pot off the flame stove and quickly start to pour slowly into the mold. Be sure to wear all of your safety gear. Once you have finished pouring out the lead place the iron pot in a safe place away from children so it can cool down.
Let the mold cool down slowly and naturally. Don’t put water on your mold as it could crack it. It should be safe to handle in a few hours.
Removing the lead item from the mold
Sometimes a little persuasion is required to jimmy the item out of your mold. I like to use a flat head screwdriver and slowly work the edges. It will pop right out. Use a small file to shave off any sharp edges. Some sandpaper will bring it up to a nice smooth surface.
I did find that the internal lead belt holes were slightly too small for the webbing to fit through but a Dremel soon made quick work of that. I guess you could also use a drill with a small 1/4 bit.
As far as I’m concerned it looks and functions just like the real dive belt weight. It is nice to be able to make a product for free just by using some common sense and some household items.
Fishing Sinker Molds
The same process is for making lead fishing sinkers. But we will use a ready-made mold.
These molds made by a company called Do-It Molds are great. All you have to do is close up the mold and pour in the liquid lead. Wate a few minutes and then open them up. Drop out the sinkers and start the process again.
Let me know in the comments below what else you have made out of lead in your DIY concrete molds.