P-O'd at paste solder

I usually solder with pallions and wire, but recently decided to try
paste solder again. I’m really unhappy because I figured, “Oh, it’s
just solder, it’s a fairly simple join (two small 1.5”-2" sections of
curved tubing), and I’m in control here." But, something happened and
my joint is less than the perfection I expected.

The problem wasn’t getting the paste solder to flow-it flowed the
way it should. Instead, I ended up with crusty “flowed” solder all
through my perfectly constructed and clean joint. That is to say, you
know how regular solder flows really nicely, and if it’s done right
you see that beautiful, smooth line (for lack of a better way to
describe the final form of the solder) connecting the joints-this was
NOT a cleanly soldered join by any means.

I still maintain that I didn’t have any problems with the paste
process or actual application of the paste. The crud I’m talking
about is the solder IN the joint–it looks really crappy and it’s
going to take a lot more work than I had planned to try to file away
this crusty, unevenly-flowed solder.

[By the way, any tips for filing the solder smooth at the point of
the join? I don’t want to mess around with the curvature of the two
tubes. I’m tempted to just scrap it and do it all over but I really
don’t want to because everything else was so perfect.]

What on earth could I have done wrong? I love the ease of working
with paste solder, but I am certainly not liking the messy-looking
end result.

Thanks in advance for any tips.

Tamra Gentry

The crud I'm talking about is the solder IN the joint--it looks
really crappy 

It’s hard to say without seeing it, but the problem of cruddy-looking
paste solder joins, in my experience, is usually because of stopping
heating a bit too soon. Paste solder seems to have a stage that
snippets don’t. I believe this is because there are many tiny grains
that are melting instead of one big one. You have to heat enough for
everything to flow together. I suggest that you pickle (I would guess
you already did), rinse, re-flux and re-flow the solder. Hold the
heat a moment longer than you’re used to and I’m betting it will all
smooth out.

I have also found that paste solder has a tendency at times to leave
more mess where it originally sat than a snippet, becuse it is
initially spread over a larger area along with its own flux. So it is
probably best to reserve paste for those situations where nothing
else will do as well-- where gravity won’t hold the snippet in place
and pick soldering too difficult, or what (I think) it does best–
cling to the inside of an area you don’t really have access to, like
when you solder two halves of a bead together.


This is only my theory based on observation, not on lab experiments,
so take it for what that’s worth.

Paste solder is essentially hundreds of tiny solder spheres that in
order to flow along a seam must come together into a single or just a
very few masses. So what happens is you get localized flow that maybe
extends (for the sake of argument) one or two MM. All of these
localized flows have to link up and become one long fluid body in
order to get that smooth bright contiguous look, which as you
complain doesn’t seem to be happening. At the junction of each
localized flow there is a dimple of sorts. Too many dimples and you
get that rough look.

Capillary action only works well when there is a reservoir from
which to draw more fluid. And that would be a suitably sized ball of
molten solder. Its the surface tension in the reservoir (ball) that
pushes the solder along the seam towards the heat, my guess is that
the torch weakens the surface tension at the leading edge of the
flow, allowing the reservoir to fill it, like a balloon animal. I’m
not a physicist but this seems to make sense to me.

Paste solder has its applications, mostly for small easily melted
structures, (hollow chain for example). Its not good for anything
structural. It can be done of course, usually by a more liberal
application of paste and more heat with a rapid back n forth torch
motion to encourage uniform flow, but its iffy at best and you run
the risk of overheating which will put you back in the spot of having
a rough fillet so what have we gained?

One of the earliest lessons I learned is that the hard way is the
easy way. Shortcuts usually have shortcomings.

Well, i’ve found dramatically different result with different brands
of paste solder, for one thing. But it almost sounds like you’ve
gotten incomplete flow of the solder if you’re seeing something that
looks “crusty.” Have you tried fluxing and re-flowing? I’d try that

Karen Goeller

The problem could be the flux in the paste solder. Try applying your
regular flux to the joint and remelting the solder. If there is
porosity in the seam then adding a small amount of your regular
solder may help to sort it out.


Hi Tamra,

Someone else recommended fluxing well and using a bit of your normal
solder, and I would have to agree. I HATE paste solder. I ended up
with a couple of tubes of it for Argentium, and my husband and I
burn off all of the binders and “flux” and junk and just use the
little balls with our regular flux. I’m eager to get through the
tubes so I can justify buying sheet again. I’d definitely say that it
can’t hurt to experiment if you’re thinking about scrapping anyway.

Good luck!

I used to work for a woman who loved paste solder! she used it as a
design element, she would smear lots of it on the surface of a piece
and build it up. Very organic looking, kind of cobwebby effect. I
don’t think she ever used it ato solder things together though.

Candy in still beautiful Central Oregon

she would smear lots of it on the surface of a piece and build it
up. Very organic looking, kind of cobwebby effect. 

I don’t think you’d get away with that in the UK, unless it’s plumb
paste solder (if there is such a thing). It would not be hallmark-
able. But interesting nonetheless. Was it similar to reticulation?


Paste Solder is not well understood. It is all based on what you
were initially trained with. I find it maligned by those not knowing
how to use it. We are all too often creatures of habit, and upset
when that comfort zone is breached.

In my locker, I have solder in the following forms, from hard down
to easy. Wire, sheet, and paste. I use each and every one of them
depending on what I am working with. I look upon all of them as
paths to the end.

I was taught Chain Making by Jerry Harr, and still have some of the
Paste Solder bearing his name, oh so many years later, and still
usable. I bought wire, when I read that it was easy to reshape and
use, so I roll it through the rolling mill, form it into tiny balls,
and shape it to the inner bezel form. It all works!

Jay Whaley teaches with sheet solder, and I use that, along with
everything else I have. Does he raise an eyebrow, better believe it.
I also save my silver filings, and when there is a resistant gap, I
mix the filings into the paste and blast away.

The real lesson is to go in with an open mind. Preconceived notions
of failure, lead to exactly that. It is all on the market because
enough trained smiths use it in one form or another. Were there a
failure to sell, the product will disappear. The market will see to

I am waiting to use up all that I currently have, and then buy from
Beth Katz of My Unique solutions, and and add Powder Solder to my


Paste solder is a great tool for some joins. I make a small dot on a
scrap piece of plastic and use a toothpick to put it on as I find
the most trouble comes when using too much solder. I always wear a
mask when polishing, soldering, and casting. Of course I already have
COPD from growing up with a heavy smoker so I know that lung
protection is not something to get lazy about!

Sorry just thought I would mention it cause I saw the what is a
collector for question and cringed. My friends call me 'darth vader’
when I am casting between the safety goggles and mask and I take it
good naturedly and say better to look like this than the