correct way to use alum any advice please

[quantieme]

hi, i have a broken screw and have tried the usual methods but to no avail so i have bought a 100 gram bag of alum but having never used it before i wondered what the correct method is. the plate is silvered brass from a pocket watch so do i soak the whole plate or just the part with the broken screw and what would be the quantity of alum to water, any advice appreciated, thank you.

[Tudor]

Subscribing to learn about it too!

[vinn3]

alum and penetrating are both used for a broken screw.  vin

[anilv]

First make sure the part you want to remove is steel and not any other metal. Also make sure no other steel parts are around as the alum is indiscriminate.

Next mix Alum with hot water and soak the part, after several hours try to scrape the broken screw out with a sharp pick, you will find it has turned to a rust like substance.

Repeat again after a few hours. Depending on the amount of alum dissolved you may need to mix a fresh batch. Most guys say that heat helps, personally I am in the tropics and haven't had to reheat, but mine usually takes around 6-10 days to get out completely. Heat may help but I can wait.

Anilv

[frenchie]

Once you are sure the only steel part is the one you want to remove, mix as much alum as will dissolve in a small container (I use a tiny glass jar). I try to keep mine warm in a double boiler on very low (you want the solution warm, not hot), it allows more alum to dissolve in the water. After a couple of days, the broken screw will be gone. I usually only do this on weekends so I can keep an eye on it, and add water if necessary. Starting on Friday evening, the screw is usually gone by Sunday. 

If you don't heat it up, you may have to wait a bit longer as mentioned above. You will see the steel part turn black in a few hours, that's a sign that it's working. Be patient, an it will work.

[quantieme]

10 hours ago, anilv said:

First make sure the part you want to remove is steel and not any other metal. Also make sure no other steel parts are around as the alum is indiscriminate.

Next mix Alum with hot water and soak the part, after several hours try to scrape the broken screw out with a sharp pick, you will find it has turned to a rust like substance.

Repeat again after a few hours. Depending on the amount of alum dissolved you may need to mix a fresh batch. Most guys say that heat helps, personally I am in the tropics and haven't had to reheat, but mine usually takes around 6-10 days to get out completely. Heat may help but I can wait.

Anilv

thank you anilv will give it a go.

[quantieme]

30 minutes ago, frenchie said:

Once you are sure the only steel part is the one you want to remove, mix as much alum as will dissolve in a small container (I use a tiny glass jar). I try to keep mine warm in a double boiler on very low (you want the solution warm, not hot), it allows more alum to dissolve in the water. After a couple of days, the broken screw will be gone. I usually only do this on weekends so I can keep an eye on it, and add water if necessary. Starting on Friday evening, the screw is usually gone by Sunday. 

If you don't heat it up, you may have to wait a bit longer as mentioned above. You will see the steel part turn black in a few hours, that's a sign that it's working. Be patient, an it will work.

thank you, i have plenty of time so will try it out, is it best to soak the whole plate or just the part with the screw.

[Gary]

I just used Alum to remove a broken screw crown screw in this thread. I put 2 teaspoons of Alum to 5 tablespoons of water. I did have to heat the mixture. I sat it in a stainless steel dish on a heating pad. Within two days the screw was gone. With the heat I kept adding a tablespoon of water every 10-12 hours.

Good luck and as others stated any ferrous material will be damaged so be mindful!

Marvin repair and service 

https://www.watchrepairtalk.com/topic/8652-banking-question-not-certain/

 

[quantieme]

6 hours ago, Gary said:

I just used Alum to remove a broken screw crown screw in this thread. I put 2 teaspoons of Alum to 5 tablespoons of water. I did have to heat the mixture. I sat it in a stainless steel dish on a heating pad. Within two days the screw was gone. With the heat I kept adding a tablespoon of water every 10-12 hours.

Good luck and as others stated any ferrous material will be damaged so be mindful!

Marvin repair and service 

https://www.watchrepairtalk.com/topic/8652-banking-question-not-certain/

 

many thanks, i now have enough info to give it a go

[Blacklab]

Slightly off watches, but having used this method successfully on broken stems in crowns in the past, I have moved onto larger items, namely removing a broken steel bleed nipple (circled, under the cloud of bubbles) from an aluminium motorcycle disc brake calliper. Not quite there yet after about 5 hours of gentle simmering, but heat certainly speeds things up...

Note the item is placed in the alum solution within a glass pyrex bowl or it would eat the steel saucepan!

[Tudor]

That’s taking it to the next level!

[p2n]

I did this recently - made a hot solution of alum. Kept adding crystals until they wouldn't dissolve - so a saturated solution. Put the brass watch plate with broken steel screw in and put the lot in the ultrasonic. Left to cool. Checked the next day and reheated solution and repeated. Took a few days to dissolve the screw but it worked in the end.

Before

During - still a few bits left

After - all gone

 

[frenchie]

On 4/17/2018 at 7:57 AM, quantieme said:

thank you, i have plenty of time so will try it out, is it best to soak the whole plate or just the part with the screw.

Soaking the whole thing is usually easier, but as long as the steel part is submerged, you're all set.

[Deggsie]

First make sure the part you want to remove is steel and not any other metal.

Actually, the screw needs to be more closer to iron than a steel alloy for the reaction to be effective. For example if the screw is stainless steel the reaction just will not happen. So the older the movement the better your chances. Chromium, manganese and stainless steels weren’t around in the good old bad old days.

Make the solution as concentrated as possible by adding more and more alum to the boiling water until no more will dissolve. The reaction is faster if the alum solution is kept warm.


Sent from my iPhone using Tapatalk

[Blacklab]

After a total of about 50 hours of simmering in alum solution the bleed screw finally dissolved - the same area circled on the new screw measuring 12x6mm, with no adverse affect on the aluminium calliper:

No drilling, damaged threads or seat, it goes to show how useful the skills learnt from watch making can be.

[quantieme]

thanks for all the advice, i have now successfully removed the screw, i soaked it for 3 days in an unheated solution and i have to say i was a bit sceptical as these things never seem to work for me but i checked it yesterday and it had gone black and just dissolved into mush, there was no damage to the thread or plate and i now have a new part and screw fitted.