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