Removing Fluxite paste flux residue

Apologies if the answer to this query appears elsewhere. Having gone through the forum and searched the net I haven't found a satisfactory solution to my specific problem. The astounding breadth of knowledge on here suggests that I am most likely to find the definitive answer within this forum.

In addition to some bodging attempts at model engineering I also dabble in 2mm to the foot railway modelling. That involves soldering a lot of nickel silver and brass and my preference for thirty years has always been Fluxite. The gunginess aids positioning and it simply seems to have more bite than any of the various alternative liquid fluxes. Much like marmite I am still on the same 30 year old tin.

Solders are usually in the 145 to 190C range.

Having made a model, often with protruding and delicate parts in the 5 to 10 thou range for handrails or crane booms etc. the received wisdom is to scrub with a stiff brush with vim or equivalent abrasive cleaner in hot water then rinse with cold and air dry.

A lot of my work either won't withstand that treatment or has sealed pockets that prevent any 'scrubbing' even if I could. This inevitably leaves a residue that can seep out over time and attack paintwork. Some professional model painters now refuse commissions if paste fluxes have been used for this reason.

So my question centres on whether there is a solvent that can be used to flush away paste residue? I have tried a huge variety of concoctions over the years using hot water and/or ultrasonic cleaners but never get 100% satisfaction. Not much of a problem for run of the mill models but a pain when one occasionally goes well and I want to do it justice.

Experiments have included the following either singly or in a soup to see what happens - cif, vim, dishwasher liquid, petrol, caustic soda, washing up liquid, barbecue cleaner, oven cleaner and virtually anything that says abrasive or cleaner in the aisles of the supermarket. All have been tried with a stiff brush and/or ultrasonic and/or multiple re-cleaning attempts.

Maybe worth mentioning that I use a glass fibre brush which leaves a lot of greasy, pasty fibre glass chips to remove so ultrasonic and detergent usually features in the mix.

The models ought to withstand boiling water so maybe someone can recommend a' hot flush' solution to get into the nooks and crannies.

Any thoughts or guidance gratefully received.

Andrew

Hi, I found this which seems to be what you're after. According to the safety data sheet here it's a 50/50 mixture of toluene and isopropyl alcohol both of which are readily obtainable for you to make your own.

Many thanks. I think alcohol works with the rosin flux residues from multiform solders but doesn't work with the greasier carrier in fluorite. I say that with some confidence having tried isopropyl alcohol at varying concentrations both hot and cold and in the ultrasonic cleaner.

cellulose gunwash works well

Hi,

Have you tried using sugar soap as used in home decorating? I model in 16mm and have had some success cleaning off fluxes of both types. You may find the best way is to heat in a suitable pan. It has the advantage of not leaving any residue and can be made in a concentration suitable for your requirement. I don't know if it will discolour the surface if allowed to soak for too long but that can be tried on a piece of waste material.

Brake and clutch cleaner may work, it's a degreaser.. At about £10 a gallon you could immerse the whole model. Good luck Noel.

try the dishwasher, try a bit of scrap to start with as it can attack some metals, but I've used it on brass components

Using the dishwasher for non-domestic items is a hanging offence in our house...or worse!

Thanks guys. The hot sugar soap option sounds good. I've used it warm a few times with reasonable results. I'll curl up my toes and try a boil wash.

Brake and clutch cleaners, and most automotive degreasers, usually fail to clear all the muck away. I will certainly try a pre wash with clutch cleaner followed by the sugar soap as an experiment.

Many thanks for your insights. Much appreciated.