The Unsung Heroes

Before you ever see the glimmer of gold on a piece, there’s a silent, liquid army at work. Solvents don’t get the glory of a shimmering metallic finish, but without them, everything falls apart, literally. They’re the difference between a lumpy, frustrating mess and a level, perfectly flat lustre coat.

Why Solvents Matter

Solvents are more than just carriers. They:

• Dissolve tricky chemicals so they can react cleanly

• Control the pace of drying to prevent dust, streaks, or uneven films

• Allow careful manipulation of viscous, waxy, or oily mercaptides and fluxes

• Help isolate and control other chemicals with minimal loss

In short, a good solvent keeps the chemistry obedient and your glaze usable.

Chloroform: The Gold Collector

When making gold thiols, chloroform earns its stripes. Gold thiols adore it: they dissolve effortlessly and form their own separate layer from the aqueous phase. That separation is golden (pun intended) because it lets you isolate the gold compound with minimal loss. The bonus doesn’t stop there, once your gold is formed, you can keep topping the beaker with fresh, clean water and stirring away all the lingering impurities: leftover methyl sulphide, excess mercaptan, and any other unruly byproducts still clinging to your precious gold. These happily leave the chloroform layer and migrate to the water layer.

Methanol: The Gold Whisperer

Once your gold thiol is happily dissolved in chloroform, it’s time for methanol to step in. Methanol doesn’t dissolve the gold thiol the way chloroform does, instead, it encourages the gold to leave the liquid and form a solid or semi-solid layer. Think of it as politely asking the gold to step out of the pool and stand on the deck, whilst the chlorofrm happily mixes with the methanol to be carried away.

Depending on the type of mercaptide, this can either be a clean filterable solid (common with aryl mercaptides) or a waxy, oily mass that’s best left to settle and decant. Either way, methanol helps isolate your gold compound from the chloroform and wash away the remaining stuff the water washes missed. A few subsequent washes with cold methanol ensure your gold is as clean as it can get before moving on.

Chemists call this type of process liquid-liquid extraction (for the initial separation from water and chloroform) and precipitation (for coaxing the gold out with methanol). It’s a classic move in the world of organic and organometallic chemistry, but here it’s all about collecting your gold with minimal losses and cleaning it to the highest degree possible.

Toluene: The Flashy Performer

Toluene shows up for bismuth and rhodium. It’s a powerhouse solvent that dissolves these metals quickly and cleanly. Then it vanishes, flashing off almost immediately from the applied lustre. The result? Immediately thickens the lustre after application ensuring it stays exaclty where your brush left it. In my recipe I only use minute amounts as it can be an unruly companion.

Cyclohexanone: The Well Behaved Companion

Cyclohexanone is the slow and steady hero of the final lustre stage. It dries at just the right speed, allowing a thin, uniform coat to form before the surface picks up dust or loses its integrity. Fast enough to be practical, slow enough to stay smooth, it’s the sweet spot between fast and slow

Acetic Acid (a.k.a. Essence of chip shop)

Acetic acid straddles a strange line in the solvent world. On the one hand, glacial acetic acid is a perfectly respectable polar protic solvent in the world of chemistry, happy to dissolve a decent range of organics and play nicely with water or alcohols. On the other, it’s not content to just sit back and watch reactions happen; more often than not, it insists on joining in.

In the bismuth trials, acetic acid wasn’t just the medium, it was the chef, converting bismuth salts into bismuth acetate before the real reaction could even start. This “double agent” nature makes it less predictable than, say, your straight-laced alcohols. It can be the solvent, the reagent, or both, depending on whether it feels like helping or hijacking.

In Summary

Solvents may not sparkle, but they’re indispensable:

• Chloroform isolates gold with minimal loss

• Methanol removes the chloroform and polishes up the end product

• Toluene dissolves tough metals and leaves no trace

• Cyclohexanone ensures a perfectly level, dust-free film

• Acetic Acid converts, solvates and catches you nose from 3km

During the journey I managed to amass a huge selection of solvents, by far from a laymans perspective they appear to be the backbone of inorganic chemistry, for every reaction or process there is a perfect solvent for the job.