Colour change from tannin bleed

Waterborne finishes on high-tannin species (Blackbutt, Tallowwood, Ironbark) can reactivate tannins in the first 24 hours and leave dark streaks that telegraph through the cured film. The controlled answer is Bona Intense primer and disciplined coverage — not a heavier topcoat.

Mechanism

Bona's Primers DL Brochure (Ed4 09/24) and Bona Intense Primer TDS (Feb 2022) both state the 'phenomenon known as tannin bleed' is caused by tannin in high-content species being solubilised by waterborne primers and carried up into the film. Bona Intense 'reduces tannin bleed in high content species' and is 'specifically recommended on timber species with high tannin content such as Blackbutt and Tallowwood'. Bona Classic and Classic UX are explicitly NOT recommended on Blackbutt or Tallowwood; Bona White is not recommended on high-tannin or darker timbers at all.

Risk profile by species

SpeciesRiskNote & source
Blackbutt high-tannin Explicitly named in the Bona Classic, Classic UX and White Improved Formula TDSs as a do-not-use species for those primers; Bona Intense is the recommended primer.Source: species_primer_matrix.json (Bona_Classic_TDS_AU.pdf + Bona_Classic_UX_TDS_AU.pdf + Bona_White_Improved_Formula_TDS_AU.pdf)
Tallowwood high-tannin Explicitly named alongside Blackbutt in the Bona Classic and Classic UX TDSs as do-not-use; Bona Intense recommended.Source: species_primer_matrix.json
Western Australian Blackbutt high-tannin Shares common name and tannin behaviour with Eucalyptus pilularis; Bona's rule is inclusive. Treat as high-tannin.Source: species_primer_matrix.json
Ironbark high-tannin FPC WA PDF: Ironbark bark has tannin content of 40% or more; sap and heartwood pigments produce strong tannin bleed risk under waterborne coatings. Bona Intense preferred; Classic/Classic UX/White all not recommended.Source: species_primer_matrix.json + fpc-species-information-western-australia.pdf
Jarrah medium-high-pigment Red heartwood timber; Bona Intense is suitable but coverage rate of 8 m2/L must be observed to avoid colour variation. Bona White not recommended on red timbers.Source: species_primer_matrix.json (Bona Intense TDS)
Brushbox medium-pigment Bona Intense suitable with 8 m2/L coverage discipline; Brushbox is not categorically excluded from Classic/Classic UX but trial application recommended.Source: species_primer_matrix.json (Bona Intense TDS)
Spotted Gum low-medium WoodSolutions datasheet rates Spotted Gum as 'minimal staining timber... less prone to bleed-through of tannins than other species'. Bona's high-tannin exclusion does NOT categorically apply; trial still required on darker sourced stock.Source: spotted-gum-woodsolutions.html + species_primer_matrix.json

Mitigations

  • prime-intense
    Specify Bona Intense as the primer on any Blackbutt, Tallowwood or Ironbark job. Do not substitute Bona Classic or Bona Classic UX.
    Source: Bona_Classic_TDS_AU.pdf + Bona_Classic_UX_TDS_AU.pdf + Bona_Primers_DL_Broch.pdf
  • prime-intense
    On Jarrah and Brushbox, observe the Bona Intense coverage rate of 8 m2/L; wider coverage risks visible colour variation.
    Source: Bona_Intense_Primer_-_Technical_Data_Sheet.txt p.1
  • Trial application on all darker-sourced Spotted Gum batches before full-floor commitment; Bona does not categorically list Spotted Gum × White, so trial is essential.
    Source: species_primer_matrix.json
  • prime-whitecraft-oil-2k
    For a 'whitewashed' appearance, Bona White + Bona Craft Oil 2K White combinations are limited to pale low-tannin species; do not specify on Blackbutt or red species.
    Source: Bona_White_Improved_Formula_TDS_AU.pdf

Bona product guidance

  • prime-intense
    Recommended on high-tannin species (Blackbutt, Tallowwood). Suitable on Jarrah/Brushbox with 8 m2/L coverage discipline. Reduces tannin bleed in high-content species.
    Source: Bona_Intense_Primer_-_Technical_Data_Sheet.txt + Bona_Primers_DL_Broch.pdf
  • prime-classic
    Not recommended on Blackbutt or Tallowwood. Should not be used on high-tannin timber species.
    Source: Bona_Classic_TDS_AU.pdf
  • prime-classic-ux
    Not recommended on Blackbutt or Tallowwood. Ideal primer to use with Bona Traffic HD Raw, but not on high-tannin species.
    Source: Bona_Classic_UX_TDS_AU.pdf
  • prime-white
    Not recommended on darker or red timbers, and not recommended on high-tannin timbers. Blackbutt specifically flagged in Improved Formula TDS as tannin-bleed risk.
    Source: Bona_White_TDS_AU.pdf + Bona_White_Improved_Formula_TDS_AU.pdf

Gaps in the corpus (no claim made)

  • No quantified 'tannin content %' per species in the Bona corpus (FPC gives Ironbark bark figure only).
  • Bona does not publish a time-to-bleed or re-bleed-probability number; the rule is categorical (species × primer).
Sources