How do you start a custom formulation when no product meets spec?

This method covers industrial custom formulations made by blending known raw materials, such as lubricants, cleaners, coatings and process fluids. It does not replace the development path a regulator sets for drugs, food, cosmetics or pesticides, and it stops at the first bench batches, before scale-up and production validation.

What do you need before you start a custom formulation?

Before you start a custom formulation, you need five inputs in writing: the application conditions, the reason existing products failed, the documents for each candidate raw material, the markets the product will be sold in, and the person who signs off the brief. A missing input turns into a guess inside the first batch.

• Application conditions: substrate, temperature range, contact materials such as seals, dilution and application method.

• Failure evidence: which specification line each off-the-shelf product missed, with the test result.

• Raw material documents: the current technical data sheet and safety data sheet for each candidate.

• Markets: where the product will be placed on the market, because classification rules are set per jurisdiction. In Great Britain, manufacturers, importers and downstream users must classify mixtures before placing them on the market (GB CLP Regulation 1272/2008, Article 4); in the US, mixtures are classified under 29 CFR 1910.1200 (OSHA, 2026).

• Sign-off: one person on the customer side who agrees that the brief describes the job.

A brief built from a phone call often changes after the first sample, and each change resets the bench work.

How do you turn a customer requirement into a measurable formulation brief?

You turn a customer requirement into a measurable formulation brief by rewriting each requirement as a property, a target or limit, a test method and a test condition, then ranking it as must-have or nice-to-have. A requirement that cannot be written this way is not ready for the bench.

ICH Q8(R2) gives a useful model from pharmaceutical development: the quality target product profile, which it defines as "A prospective summary of the quality characteristics of a drug product that ideally will be achieved to ensure the desired quality, taking into account safety and efficacy of the drug product" (ICH Q8(R2), 2009). Prospective is the point. The brief is fixed before results exist, so results are judged against it rather than the other way round.

The table below shows how vague requirements become brief lines; the targets are illustrative.

The first row is typical: "must not rust" becomes a pass or fail on a named coupon and test. NIST also advises that "All of the objectives should be written down, even the 'unspoken' ones" (NIST/SEMATECH e-Handbook, section 5.3.1), so ask what the customer will check without telling you.

What role does each ingredient play in a custom formulation?

Each ingredient in a custom formulation should have one written role tied to a brief line: base or carrier, performance additive, stabilizer or preservative, processing aid, or adjuster for pH, viscosity or appearance. An ingredient without a role is a candidate to remove; a role served by two ingredients is an interaction to test.

ICH Q8(R2) asks for the same discipline in drug products: the excipients chosen and their concentration "should be discussed relative to the respective function of each excipient", including "all substances used in the manufacture of the drug product, whether they appear in the finished product or not (e.g., processing aids)" (ICH Q8(R2), 2009). The rule transfers to industrial blends, where a defoamer is easy to forget.

Write the role list in four columns you can copy: ingredient, role, brief line it serves, and what you expect if it is left out. If you cannot fill the last column, you cannot explain a failed batch.

Mark pairs that might interfere. ICH Q8(R2) states that compatibility of excipients with other excipients, where relevant, "should be established" (ICH Q8(R2), 2009). Two surfactants of opposite charge are a typical pair (illustrative). Each marked pair becomes a bench compatibility check.

What does a mass balance check catch in a custom formulation?

A mass balance check on a custom formulation catches totals that do not reach 100 parts, active levels counted on the wrong basis, water or solvent hidden inside raw materials, and losses or reaction products that change the final composition. Run it on paper before the first batch and again after weighing.

In a mixture, the component proportions "must sum to one" when expressed as fractions of the mixture (NIST/SEMATECH e-Handbook, section 5.5.4). Raising one ingredient therefore lowers another.

Four checks:

1. Total: every line adds to 100 parts by mass, including processing aids.

2. Basis: actives are entered as supplied and as active. A 40% active solution added at 5 parts delivers 2 parts active and 3 parts carrier (illustrative).

3. Hidden carriers: water or solvent inside raw materials is added to the stated water or solvent line.

4. Losses and reactions: volatile loss during heated mixing is weighed, not assumed. OSHA defines a mixture as two or more substances "in which they do not react" (OSHA, 2026); if two ingredients react, as an acid and a base do, record the product formed.

How do you review compatibility, process and safety before the first custom formulation batch?

You review compatibility, process and safety before the first custom formulation batch by reading the handling, storage and reactivity sections of each raw material's safety data sheet, checking the addition order and temperature against them, and deciding who classifies the finished mixture.

Compatibility starts in the safety data sheet. Under the US format, section 7 covers conditions for safe storage "including any incompatibilities", and section 10 covers the possibility of hazardous reactions and incompatible materials (OSHA, 29 CFR 1910.1200 Appendix D, 2026). Read both for every raw material and the marked pairs.

Process fit asks whether the plant can repeat the bench method: addition order, mixing time, shear, heating and cleaning.

Safety steps belong in the bench plan itself. Before you heat a batch or add an acid, alkali or oxidizer, read the safety data sheet sections 7 and 10 for each raw material involved and follow the workplace's hazard communication program under 29 CFR 1910.1200 (OSHA, 2026), or the local equivalent.

Classification comes before shipping a sample. US manufacturers classify mixtures following Appendices A and B of 29 CFR 1910.1200 (OSHA, 2026), and in Great Britain the manufacturer, importer or downstream user classifies it under GB CLP before placing it on the market (GB CLP Regulation 1272/2008, Article 4; HSE, The GB CLP Regulation).

Which bench trial pass and stop criteria should a custom formulation have?

A custom formulation should have a pass criterion for every must-have brief line and a stop condition for each, written down before the first batch is weighed. Criteria set after results are seen tend to move toward whatever the batch achieved.

The table below decides, for each check, whether to iterate, change the brief or stop; limits are illustrative and come from your own brief.

The first row carries the stop rule that matters most: a target missed widely after a fixed number of rounds means the brief or the raw material set is wrong, not that more batches are needed. NIST's checklist adds two habits: "Preserve all the raw data--do not keep only summary averages!" and "Record everything that happens" (NIST/SEMATECH e-Handbook, section 5.1.3). Keep each batch's weights, addition order, temperatures and observations with its result, so a failed batch can be compared with a passing one line by line instead of from memory.

Common custom formulation mistakes

The most common custom formulation mistakes are starting without a fixed brief and judging batches against criteria written afterwards. Six come up again and again.

• Starting from a supplier's starting-point formula before the brief exists.

• Changing one ingredient at a time over many rounds. In a mixture every change shifts the other proportions (NIST/SEMATECH e-Handbook, section 5.5.4); a designed experiment that changes several ingredients at once, planned in advance, maximizes the information gained for a given experimental effort (NIST/SEMATECH e-Handbook, section 5.1.1).

• Leaving processing aids out of the role list and the mass balance.

• Entering actives as supplied when the brief states them as active, so the batch has less active than intended.

• Treating the safety data sheet and classification as a shipping task. A raw material swap at that stage restarts the bench work.

• Keeping only averages. Spread between batches can be the first sign that a process step, not the formula, is the problem.

Each has the same fix: write the decision down before the batch.

When should you call a formulation specialist about a custom formulation?

You should call a formulation specialist about a custom formulation when the brief needs a chemistry you have no raw material experience with, when ingredients react rather than blend, when the target market's classification is unclear, or when a stop condition has been hit twice. In each case another batch will not answer the question.

Regulated end uses need a specialist from the start. Food contact, drinking water, cosmetics and medical products have their own approval routes, and an industrial bench plan does not cover them.

Bring the specialist the written brief, the role list, the mass balance and every batch record, including the failures. Lubinpla's formulation design work follows the same order: it fixes a measurable brief, reviews candidate formulations for compatibility, process and safety, and issues the first bench trial plan as one document for your review.

Agree in advance who signs off a brief change and who owns the classification.