Bacteriostatic water — often shortened to BAC water — is a sterile diluent commonly used in laboratory settings to reconstitute lyophilised (freeze-dried) research materials. It is included with every peptide order at Peptidverket so the supplied formulation can be brought into solution under controlled, repeatable conditions. This page gives a clear, neutral overview of what BAC water is and how it is handled in research environments.
What BAC water is
BAC water is sterile water that contains a small amount of benzyl alcohol — typically around 0.9% — added as a bacteriostatic preservative. The result is a clear, neutral solution intended as a diluent for lyophilised materials in laboratory work. It is supplied in sealed multi-dose vials so small volumes can be drawn without compromising the sterility of the remaining contents.
Why it is used in research
Lyophilised research materials are stored as a dry powder for stability, but most analytical and laboratory work requires them in solution. BAC water is widely used as the diluent because it is sterile, well characterised, and slows microbial growth in the vial between uses. This makes it well suited to multi-step research workflows where the same vial may be sampled repeatedly over a short period.
How it differs from regular sterile water
Plain sterile water (such as sterile water for irrigation) contains no preservative. Once opened, any microbial contamination introduced into the vial can grow freely, so plain sterile water is generally treated as single-use. BAC water differs in one key respect: the added benzyl alcohol acts as a bacteriostatic agent, meaning it slows bacterial growth inside the vial. That is the main reason BAC water is preferred over plain sterile water when the same vial is accessed more than once.
The preservative: benzyl alcohol
The preservative in BAC water is benzyl alcohol, a well-characterised compound used at low concentration specifically for its bacteriostatic effect. It does not sterilise the water further, but limits the growth of common contaminants between uses. The presence of benzyl alcohol is the defining difference between BAC water and plain sterile water.
Storage basics
Unopened BAC water vials are typically stored at normal room temperature, dry and protected from light. After the vial seal is first punctured, it is normally kept refrigerated and used within the timeframe stated by the supplier. Vials should always be inspected visually before use; any solution that looks cloudy, discoloured or contains particles should be discarded.
Why it is included with peptide purchases
Every peptide order at Peptidverket ships with one vial of BAC water so the lyophilised material can be reconstituted as soon as it arrives, without sourcing a separate diluent. It is supplied as a convenience for laboratory workflows and is documented as a research-grade diluent only. As with the peptide formulation itself, BAC water is supplied for controlled laboratory environments and is not a consumer product.
References and documentation
Each batch supplied through Peptidverket is documented with a certificate of analysis covering identity, purity and appearance. Researchers are encouraged to consult peer-reviewed primary literature for detailed pharmacological discussion and to validate analytical assays against their own controls.
Related product
View the corresponding research-grade product in the catalogue: BAC Water 10ml →
This page is provided for general research context only. BAC water is supplied as a research-grade diluent for controlled laboratory environments. It is not a consumer product, is not formulated for human or veterinary use, and no therapeutic claims are made.