My Candles Are Stable During Winter but Develop Off-Notes During Summer — Should I Investigate Seasonal Storage Conditions?

Why a seasonal pattern points to storage

You make the same candle all year. Winter batches smell as they should for months. Summer batches pick up something you did not put there — a sour edge, a sharp or solvent-like note, a flat or slightly stale opening. When a fault follows the calendar rather than the oil lot or the wax lot, the first suspect is temperature, because temperature is what changes most between seasons in a non-AC workshop.

As general fragrance practice, heat and oxygen are the usual drivers of oil ageing, and they work together: warmth speeds the reactions that oxygen starts. Lighter, fresher materials — many citrus and green top notes — tend to change first. That is why a lemon or bergamot candle often shows a summer problem before a woody or vanilla one does. The Citrus Lemon page itself says citrus top notes are volatile and fade faster than warmer families.

But a summer off-note can enter at two very different places, and you need to know which before you fix anything.

Two suspects: the bottle and the shelf

The first suspect is the oil in the bottle. A 1 kg bottle that is opened twice a week through April, May and June meets warm air and fresh oxygen every time, and the headspace grows as the level drops. If that oil has changed, every candle you pour from it carries the change from day one — no matter how well the candles are stored.

The second suspect is the finished candle. Oil that was fine on pour day can shift inside the wax if the curing area or finished-goods shelf runs hot for weeks. In that case the bottle smells right and the candles do not.

This is where retained samples pay for themselves. A small, sealed, labelled sample of each oil lot kept cool and dark, and two or three retained candles from each batch, let you compare today's bottle and today's candles with what they were when new. Without them, you are comparing against memory, and memory is a poor reference for smell.

How to compare oil samples fairly

Bring the working bottle and the retained sample to the same room and let both reach room temperature. Dip a separate clean smelling strip in each, label the strips, and smell them side by side, then again after ten minutes and after an hour, as the top notes leave the strip and the heart and base come through. Smell only. If one sample has gone cloudy after cool storage, warm the closed bottle in warm water, mix it thoroughly and check again; cloudiness that clears is often a reversible physical change.

Measure the seasons, place by place

Put a min/max thermometer in the oil store, the curing area and the finished-goods shelf, and read them weekly through a full summer and a full winter. CSI does not sell these; any basic min/max unit will do. You are looking for the places where summer highs climb furthest above winter highs — top shelves, rooms under a metal roof, cupboards against a sun-facing wall.

Monsoon humidity is worth recording too, but be honest about what it explains. Humidity mainly affects cartons, labels and condensation on glass; it is not a direct explanation for a fragrance off-note. Heat is the stronger lead for a summer-only problem.

Protect the oil through the hot months

General good practice: keep oils sealed, upright, cool and dark, away from windows, roofs and heat sources, and open large containers as rarely as possible. Decant part of a big bottle into smaller, clean, well-sealed containers — amber glass, or whatever the supplier recommends — so the main stock is opened less often and each working bottle has less air above it. Label each decanted bottle with the oil name, lot and dates.

Pack size helps too. With Citrus Lemon, one 1 kg pack is ₹2,832.00. Two 500 g packs are 2 × ₹1,420.00 = ₹2,840.00, only ₹2,840.00 − ₹2,832.00 = ₹8.00 more, and the second pack stays sealed until you need it. Ten 100 g packs are 10 × ₹300.00 = ₹3,000.00, which is ₹3,000.00 − ₹2,832.00 = ₹168.00 more per kilogram — worth it only if your usage is very slow. CSI does not publish how its oils are packed, so check what arrives and ask us if you need to know about the container.

Size the purchase to the season. If your example usage is 250 g of Citrus Lemon a month, a 1 kg bottle opened in April lasts into July — the whole hot season with a growing headspace. Two 500 g packs halve that exposure for ₹8.00.

What to change, in what order

If the oil bottle had changed and the retained sample had not, the fix is oil storage and pack size. If the bottle was fine but summer candles drifted, the fix is the curing and finished-goods storage. If both stored well and summer candles still differ, test whether the oil simply behaves differently in your system at summer temperatures — real-time ageing in your actual summer conditions, compared with an air-conditioned set, is the evidence.

Only then consider a different oil for the summer range, and test it the same way before you buy it in quantity. CSI fragrance-oil pages publish no shelf life and no storage temperature. Ask us on WhatsApp (+91 7397976926) for the IFRA certificate, MSDS and any storage guidance for your oil and lot, and get the answer in writing. The 60-month shelf life on CSI 464 and CSI 468 is a wax statement only.

Keep notes on every summer batch: pour date, oil lot, which bottle it came from and how long that bottle had been open. When a complaint arrives in August, those notes tell you whether the candle came from a fresh bottle or one that had been open since April.

Plan the calendar around what you learn. If summer production is where problems start, consider making more of your volatile, fresh-top lines in the cooler months and holding them in your best storage, or making them in smaller, more frequent runs through summer so no batch waits long. Either choice should be backed by your own retained-candle comparisons, not by habit.

And never tell a customer a summer candle will smell exactly like the winter one. Tell them to keep it cool and out of the sun, and stand behind what you have tested.

Where this page fits

CSI already has guides that cover parts of this question. This page answers one fragrance-ageing decision; these cover the neighbouring questions:

Three things to buy for this decision

Frequently asked questions