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Soft Solder Paste

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Martin Kyte01/05/2018 09:32:19
1515 forum posts
24 photos

Hi Chaps

I'm sure many of you will have found the advantages of using soft solder paste for constructing small brass fittings for models. Does anyone have a workable way of reviving pots of paste that have partially dried out. Is there a convenient solvent to add a few drops of to the mix?

regards Martin

Clive Brown 101/05/2018 10:25:22
287 forum posts
7 photos

I've "revived" Easyflo paste with methylated spirit. Seems to work on that. Surgical Spirit or iso-propyl alcohol might do likewise. Worth a try?

Edited By Clive Brown 1 on 01/05/2018 10:25:43

J Hancock01/05/2018 12:09:08
320 forum posts

I think the soft-solder paste referred to is NOT Easyflo flux.

You could try mixing it with red Coraline paste but not sure if that would be active enough to cope with too much

surface oxide .

Muzzer01/05/2018 13:07:50
2904 forum posts
448 photos

Could you simply use plumber's flux? That's pretty active and easily available. Warm it up and it becomes quite mobile.

JasonB01/05/2018 13:19:00
16561 forum posts
1765 photos
1 articles

maybe bakers Fluid, whatever is in the paste is quite corrosive if not cleaned off really well.

Martin Kyte01/05/2018 13:50:02
1515 forum posts
24 photos

Sensible suggestion.

Bakers is mostly Zinc Chloride which is listed as the flux in the data sheets for soft solder paste. Looking up the data on Bakers No 3 suggests it's water based so maybe water could be the answer for reviving the solder paste.

This all started as a conversation with a couple of mates last night so I just wondered what you lot did other than go and buy some more when the pot dries out.

regards Martin

Clive Brown 101/05/2018 13:52:14
287 forum posts
7 photos
Posted by J Hancock on 01/05/2018 12:09:08:

I think the soft-solder paste referred to is NOT Easyflo flux.

The paste that I was referring to is Easyflo solder paste, ie a mixture of powdered Easyflo solder and flux, as marketed by JM and sold in small glass jars. No longer available of course. Could be useful for small assemblies.

My thought was that soft-solder paste might be revived in the same way.

Bob Youldon01/05/2018 15:36:55
183 forum posts
20 photos

Hi folks,

Soft solder paste can be brought back to life with a few spots of water, simples. I've done this for years and it works well.



Martin Kyte01/05/2018 16:03:38
1515 forum posts
24 photos

Aha. ~Thats the answer I was looking for.



CuP Alloys 102/05/2018 09:29:13
200 forum posts

Hi Martin,

Paste is sold in syringes or other containers that can be pressurized to expel the paste as required.

Paint is sold in small pots. To use, shake well and brush on. (See instructions on the tin!)

They are two totally different products. We need to be clear on what we have. Paste or paint

A fortune awaits he/she that simply adds soft solder powder to an aqueous solution of zinc chloride, shakes it well, and packs into syringes/pots. The world is their oyster!

But wait ....what keeps the powder in suspension and usable over time as a solder/flux combination?

What dries out of the paste or paint (soft or silver solder) is the organic binder that holds the two components together. It is immiscible with water.

Methylated spirit will only thin it and allow the solder to separate. Think gloss paint

If you want longevity from a solder paste or paint, keep it airtight in the first place.




I am sure there is some dried out paint in my shed. I've got some water, meths and a bit of paintwork that wants touching up around the house.

You wouldn't. Would you?

larry phelan 102/05/2018 10:39:54
527 forum posts
11 photos

I too have a tin of solder paste which I dig out from time to time for a small job. When I do,I usually find it has dried out hard [so would you if you were left on a shelf that long ] However ,a few drops of water works wonders,just break up the paste as best you can,then just add water and stir !. I helps if you remember to try and seal the tin until next time,although I seldom do. I think the paste I have is made by Fry,it,s in a small blue tin with a screw cap.

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