The "spray that makes lead glow" has been showing up in renovation videos and Instagram demos for the past year. Here's what's actually in the bottle, and the chemistry that makes it work.
What's in it
The active formulation is methylammonium bromide (also written methylamine hydrobromide, CH3NH3Br) dissolved in isopropanol alcohol with a small amount of acid. The chemistry was first published in 2018 by a group of Dutch scientists — Lukas Helmbrecht and Prof. Willem L. Noorduin at AMOLF, a research facility in the Netherlands.
Their paper — "Shape-preserving transformation of carbonate minerals into lead halide perovskite semiconductors based on ion exchange/insertion reactions" — appeared in Nature Chemistry, and the original application was actually solar-cell research. The lead-detection application came later, but the chemistry is the same.
Step 1 — acid frees the lead
Lead in old paint is locked into a basic lead carbonate (hydrocerussite, formula 2PbCO3·Pb(OH)2). The acid in the formulation reacts with the carbonate to release lead chloride:
PbCO3 + 2 HCl → PbCl2 + H2O + CO2 ↑
For the full hydrocerussite pigment in lead paint, the overall reaction is:
2 PbCO3 · Pb(OH)2 + 6 HCl → 3 PbCl2 + 4 H2O + 2 CO2 ↑
The freed lead is now in solution as lead(II) chloride (PbCl2), ready for the next step.
Step 2 — methylammonium bromide assembles the perovskite
The freed Pb²⁺ ions react with the methylammonium bromide to form a methylammonium lead halide perovskite:
CH3NH3Br + PbCl2 → CH3NH3PbBr3 + (mixed halides)
The product, methylammonium lead bromide (CH3NH3PbBr3), is a member of the lead halide perovskite family — the same materials being researched for next-generation solar cells. Under 365 nm ultraviolet light, this crystal absorbs UV photons and re-emits visible green light at approximately 540 nm wavelength. That's the glow you see.
Why this is a big deal
Older reagent chemistries (sodium rhodizonate, sodium sulfide) only register lead above a few hundred PPM and only on substrates where acid can dissolve the lead. The perovskite chemistry has very different properties:
- Single-particle resolution. One lead particle = one visible green dot under UV.
- Highly selective. The crystal cannot form without lead — no false positives on zinc, copper, titanium.
- Works on substrates that resist dissolution. Vitrified ceramic glaze, painted metal — surfaces where the acid in a rhodizonate swab struggles to make headway.
This chemistry — refined and reformulated for consumer use — is the basis of Fluoro-Spec, the perovskite-based lead test we sell at Detect Lead.
Key facts
- Active reagent: Methylammonium bromide (CH3NH3Br), CAS 6876-37-5
- Solvent: Isopropanol with small amount of acid
- Product: Methylammonium lead bromide perovskite (CH3NH3PbBr3)
- Excitation: 365 nm UV
- Emission: ~540 nm visible green
- Origin: Helmbrecht & Noorduin, AMOLF, 2018 Nature Chemistry
FAQ
What is the spray that makes lead glow?
Methylammonium bromide in isopropanol with a small amount of acid. Reacts with surface lead to form a methylammonium lead bromide perovskite crystal that fluoresces green under 365 nm UV.
How does it work chemically?
Acid frees the lead from carbonate (PbCO3 + 2HCl → PbCl2 + H2O + CO2); methylammonium bromide then assembles the perovskite (CH3NH3Br + PbCl2 → CH3NH3PbBr3). The perovskite emits visible green light under 365 nm UV.
Where was the chemistry first published?
Helmbrecht et al., Nature Chemistry 10:740–745 (2018), AMOLF, the Netherlands.
References
- Holtus, T. (Helmbrecht et al.) "Shape-preserving transformation of carbonate minerals into lead halide perovskite semiconductors..." Nature Chemistry 10:740–745 (2018). DOI: 10.1038/s41557-018-0064-1
- Helmbrecht, Noorduin et al. "Detection of Lead in Paint, Dust, and Soil by Simple Reaction with a Perovskite Precursor." Environmental Science & Technology (ACS), 2023. DOI: 10.1021/acs.est.3c06058
- AMOLF research institute, Amsterdam — amolf.nl