Alum

[antonyh]

Never used Alum before,  got a couple of broken screws I'm hoping to remove, how do I mix it ,is it best  hot or cold. 

I know it's not worth doing, but I'm  deturmed to  give  it go. 

[ricardopalamino]

I have used Alum with not so good results . It ended dissolving more then the broken screws and made the plate unusable . I put some grease or vaseline around the screwhole and mixed a bit of warm water and even vinegar with the alum and applied the paste on the screw . 

Then as it was drying out I added drops of warm water and had the plate under a light bulb for the warmth it needs to activate . 

I googled how to use alum for this purpose and also searched other forums . 

I have had better luck using penetrating fluid for a while alternating using my ultra-sonic cleaner to vibrate the part loose , and then either using the broken screw head to turn the screw out , but have had the best luck using some inexpensive jagged tipped screw extractors I found on Ebay . They look like screwdrivers and come in about 3 or 4 sizes .

 

 

[mikepilk]

I've had excellent results from alum. If I want to restrict the area, I make a cone of rodico around the screw. 

I dissolve a bit of alum in warm water and drop it on to the screw. A day or so later, no screw !