Every vape cartridge has a base liquid. For UK-legal low THC vapes, this base shapes vapour production, flavour, and comfort. PG, VG, and MCT are the main options, and each behaves differently in the device and the body. Here, it is also worth knowing that high-quality THC vapes might, instead, depend on terpenes, which results in an even better vaping experience.
When people talk about vape quality, they often focus on coils, batteries, or terpene blends. But none of that works without the carrier liquid. The base is the medium that dissolves cannabinoids and terpenes, carries them to the coil, and ultimately vaporises. Understanding vaping glossary can be bit intimidating, but it is worth it.
Choosing the right base is not just a matter of taste; it determines throat feel, vapour density, and even safety.
The three main bases are propylene glycol (PG), vegetable glycerine (VG), and medium-chain triglyceride (MCT) oil. Each has distinct properties.
Propylene Glycol (PG)
PG is a clear, thin liquid derived from petroleum but refined for food and pharmaceutical use. Its defining feature is low viscosity—it is thinner than VG or MCT. This makes it ideal for wicking in vape cartridges, as it saturates the coil quickly and reduces the risk of dry hits.
From a performance perspective, PG is an excellent flavour carrier. Terpenes and cannabinoids dissolve readily, and the vapour delivers a sharper “throat hit.” Some users like this sensation because it resembles traditional smoking.
The downside is irritation. A minority of users find PG harsh, particularly at higher concentrations. It can cause dryness or mild throat tickling. For this reason, PG is often blended with VG to balance smoothness and flavour delivery.
In the UK, in the low THC vapes segment, PG-based blends remain common because they offer consistency and compatibility with ceramic coils.
Vegetable Glycerine (VG)
VG is a thicker, sweeter liquid derived from plant oils such as soybean, coconut, or palm. Its viscosity is high, which makes it more resistant to wicking. Cartridges designed for VG must have efficient coils and wicks to avoid clogging.
The main advantage of VG is vapour production. It creates dense, smooth clouds with little throat hit, which many users describe as more comfortable. It also has a naturally sweet taste that can soften harsher terpene profiles.
Because of its thickness, VG does not carry flavour as effectively as PG. Terpene-rich vapes may taste muted in a VG-heavy base. Still, for those who prioritise smoothness and vapour volume, VG is appealing.
In practice, many UK legal vape cartridges use a PG/VG mix, adjusting ratios to balance flavour and comfort.
Medium-Chain Triglyceride (MCT) Oil
MCT oil is a refined fraction of coconut or palm oil, liquid at room temperature. It dissolves cannabinoids efficiently and provides a smooth, almost buttery vapour. For a time, MCT was widely used in CBD and hemp vapes.
However, concerns have emerged about inhalation safety. Unlike PG and VG, which are widely studied in inhalation contexts, MCT is primarily approved for oral use. Some studies have questioned whether heating MCT may produce unwanted by-products, and regulators have encouraged caution.
As a result, reputable UK brands now rarely use MCT in vape cartridges. When present, it is usually in low concentrations or clearly disclosed. Consumers should always check Certificates of Analysis and ingredient lists to confirm whether MCT is used.
Technical Differences in Use
From a hardware perspective, PG and VG are highly compatible with ceramic coils, which distribute heat evenly and reduce burning risk. MCT, being oilier, can stress wicks not designed for its viscosity. It also requires slightly higher temperatures for consistent vapourisation, which risks degrading delicate terpenes.
From a chemical standpoint, PG is polar, meaning it mixes well with both cannabinoids and flavour molecules. VG is less effective as a solvent but excels at generating vapour density. MCT is non-polar and dissolves cannabinoids well, but carries the inhalation uncertainty already noted.
Choosing The Right Base
For UK users of legal low THC vapes, the safest and most reliable choice remains PG/VG blends. They are proven in performance, supported by coil design, and widely used by reputable brands.
- PG-heavy blends emphasise flavour and throat hit.
- VG-heavy blends emphasise smoothness and vapour density.
- Balanced mixes aim to capture both.
MCT is best avoided unless clearly backed by safety data. Responsible brands are increasingly phasing it out, focusing instead on PG/VG systems that deliver consistency and peace of mind.
The Bottom Line
The base liquid ultimately defines the vaping experience. PG carries flavour sharply but can feel harsh. VG smooths vapour but mutes taste. MCT offers solubility but raises safety questions.
By understanding PG, VG, and MCT, users can interpret labels with confidence and select products that are safe, compliant, and enjoyable.
