Reference
Frequently asked questions
Short answers to common questions about TDA Logic, its relationship to HLB and the status of its evidence.
What is TDA Logic?
TDA Logic (Tri-Domain Architecture logic) is a placement framework for formulating leave-on cosmetics on a fixed nanoscale architecture. In that architecture three colloidal domains, the nanocolloidal (oil-core), nanoliposomal (bilayer) and nanomicellar domains, are designed to coexist in a continuous water phase under electrostatic (DLVO) stabilisation. The formulator assigns each ingredient to one of four destinations, the three domains or the water phase, using its logD at the formula’s pH, its solubility and charge, and then checks the formula against the loading budgets those assignments imply.
Who defined TDA Logic?
TDA Logic was defined by Pensive Beauty® Nanoscience Labs (2025). The name, definition and attribution are set out in a preprint deposited on Zenodo in October 2026: Pensive Beauty® Nanoscience Labs (2026). TDA Logic: The Tri-Domain Placement Logic Succeeding 1940s HLB Logic in Nanoscale Cosmetic Formulation (Version 1.0) [Preprint]. Zenodo. https://doi.org/10.5281/zenodo.23384911
How is TDA Logic different from HLB?
The two answer different questions. HLB, introduced by Griffin in 1949, is a selection rule: the formulator works out the required HLB of an oil phase and chooses an emulsifier or blend to match, and that choice builds the emulsion’s structure. TDA Logic is a placement rule: the colloidal structure already exists, so the formulator decides which destination each ingredient enters and whether each domain stays within budget. HLB takes oil-phase composition and emulsifier HLB values as inputs; TDA Logic takes logD at the formula’s pH, solubility and charge. HLB has no term for particle size, surface charge or ingredient location, which are the variables a fixed nanoscale architecture is designed around.
Does TDA Logic replace HLB?
Not in general. TDA Logic is proposed as the successor design logic to 1940s HLB logic for formulating on a fixed nanoscale architecture, a case in which the emulsifier decision has been made upstream and is no longer a formulation variable. For conventional emulsions, HLB remains the tool for selecting emulsifiers, alongside related methods such as required-HLB blending, the phase inversion temperature and hydrophilic–lipophilic deviation. The two frameworks sit side by side, and TDA Logic does not dispute HLB within the macro-emulsion setting it was devised for.
Do I calculate a required HLB when formulating with TDA Logic?
No. The architecture arrives with its interface already built, so there is no emulsifier blend to choose and no required HLB to match. The formulator also does not add solubilisers to clear oils into the water phase or apply heat and high shear to rebuild the carrier; extra surfactants would compete with the built interface and can reduce stability, so they are left out rather than optimised. This does not mean the system lacks surface-active material: a lecithin-based architecture contains phospholipids as part of its structure. It means the emulsifier choice is settled before formulation begins.
What are the domains in TDA Logic?
Three colloidal domains are designed to coexist. The nanocolloidal (oil-core) domain takes high-logP ingredients such as emollient oils and oil-soluble vitamins. The nanoliposomal (bilayer) domain takes amphiphiles that seat in a phospholipid bilayer, including lipidated peptides. The nanomicellar domain takes surface-active and solubilised ingredients. The continuous water phase is a fourth destination for humectants, glycols and water-soluble actives, but it is not counted as a domain. A domain here means a coexisting, kinetically stabilised particle population, not a separate phase inside one droplet.
Why does charge matter in TDA Logic?
The architecture is specified with an anionic surface kept stable by electrostatic repulsion, as described by DLVO theory. Anionic and nonionic ingredients are generally compatible with that surface. Cationic ingredients, polycations and multivalent metal ions can neutralise the surface charge or bridge neighbouring particles, so they are minimised or excluded whichever domain they would otherwise enter. Because the charge of an ionisable ingredient depends on pH, charge is always assessed at the finished formula’s pH.
Why are salts budgeted in TDA Logic?
Dissolved electrolytes raise the ionic strength of the water phase, which compresses the electrical double layer around each particle, shortens the Debye length and lowers the repulsive barrier that keeps particles apart. Every ion counts towards the ionic-strength budget: added salts, salt-form actives, humectant salts, chelators, neutralising counterions, pH adjusters and salts carried inside supplier blends. Multivalent ions weigh more heavily than their mass suggests, because ionic strength scales with the square of ionic charge.
Is domain partitioning measured?
No. The domain assigned to each ingredient is a design specification derived from its physicochemical properties; the fraction of each ingredient that actually resides in each domain has not been measured. Particle size (Z-average) and polydispersity index are measured by dynamic light scattering on every batch, and the loading limits are modelled. The preprint names candidate methods for characterising finished formulas, namely in-vitro tape-strip deposition, Franz diffusion cell studies, confocal Raman depth profiling and zeta-potential measurement, but reports no results from them. None of these methods measures how an ingredient partitions between domains.
Is TDA Logic peer reviewed?
No. The primary reference is a preprint, Version 1.0, deposited on Zenodo on 15 October 2026 under a CC BY 4.0 licence, and it has not been through peer review. Its design specifications and modelled limits should be read with that in mind; this site labels each claim as specified, measured or modelled so the evidential status stays visible.
What products is TDA Logic for?
Leave-on cosmetic products applied to intact skin and hair and formulated on a fixed nanoscale architecture, for example serums, lotions and creams. The framework describes how a cosmetic vehicle is physically organised. It makes no claims about treating, preventing or diagnosing any condition, and statements about how a particular finished product performs depend on its whole formula and need that product’s own characterisation data.
How do I cite TDA Logic?
Cite the Zenodo preprint: Pensive Beauty® Nanoscience Labs (2026). TDA Logic: The Tri-Domain Placement Logic Succeeding 1940s HLB Logic in Nanoscale Cosmetic Formulation (Version 1.0) [Preprint]. Zenodo. https://doi.org/10.5281/zenodo.23384911. When describing, using or adapting the framework, credit the lab and cite this record. A BibTeX entry and the full reference list are on the citation page.