PRIMER / UNDERCOAT · THE FOUNDATION
1K PLASTIC PRIMER (GREY) GP1390
GP1390
Germa-Tech 1K Plastic Primer Grey is a specially formulated single component primer. Quick drying adhesion promotion on plastic parts, grey in colour to assist with colour blending.…
SCAN FOR THE FULL RANGE,
APPLICATION GUIDES & VIDEOS
germatech.com.au
TDS v2.3 · ISSUE 02.09.2026
SUPERSEDES 09.2024
REVIEW DUE 07.2028
100 : 100 (100%) by volume - 100ml GP1390 to 100ml Premium Reducer
BY VOLUME
GRAVITY RP 1.2-1.4 mm; HVLP 1.2-1.4 mm
HVLP 1.3-1.5 bar · RP 2.0 bar
Wet Spray 2.5 coats MAX (1 light tack coat + 2 solid coats)
1-2 µm
MAXIMUM 2 µm (2.5 coats (1 light tack coat + 2 solid coats) at 1-2 µm is maximum)
10 min at 20 °C between coats (allow extra time in colder conditions)*
*ADJUST FOR THE DAY'S TEMPERATURE
01SUITABLE SUBSTRATES
- PP, PA, PE and other plastic parts
- (not on pre-primed - conduct a surface test on rear of plastic before application)
02SURFACE PREPARATION
Remove wax, silicon and other contaminants with Germa-Tech Prepsol and Anti-Static Cleaner. Wet Sanding P800-P1000. Further degrease.
03MIXING
| PRIMER | REDUCER |
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| GP1390 | GP5107/GP5107 Premium Reducer |
| Ratio by volume | 100 : 100 (100%) by volume - 100ml GP1390 to 100ml Premium Reducer |
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| Pot life | 1 hour at 20 °C |
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| Notes | The reducer column heading is printed 'GP5107/GP5107' on the sheet |
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BEFORE YOU START — THE SYSTEM IS THE PROCESSGerma-Tech abrasives and ancillary products are graded and tested for compatibility with this product and the process on this sheet — that control is what makes any problem on the job assessable and fixable. Once a non-Germa-Tech product has been used at any step, what actually touched the panel can no longer be verified, and issues that arise cannot be fairly assessed — by us or by anyone. Use the system through the whole process, and if something on this sheet does not fit the job,
talk to us before you spray. Refer to the
GERMA-TECH APPLICATION STANDARD.
04APPLICATION
| Gun — gravity feed | RP 1.2-1.4 mm; HVLP 1.2-1.4 mm |
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| Pressure — HVLP | 1.3-1.5 bar |
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| Pressure — RP | 2.0 bar |
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| Coats | Wet Spray 2.5 coats MAX (1 light tack coat + 2 solid coats) |
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| Flash-off between coats | 10 min at 20 °C between coats (allow extra time in colder conditions) |
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| Dry film build | 1-2 µm |
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| Maximum film build | 2 µm (2.5 coats (1 light tack coat + 2 solid coats) at 1-2 µm is maximum) |
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05DRYING & CURING
| TEMPERATURE | DUST FREE | DRY TO SAND | NOTE |
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| 15 °C | 20 minutes | 45 hours ⚑ | — |
⚑ VALUE TO CONFIRMthe source sheet prints 45 HOURS against a 15-20 minute dust-free time; read as 45 minutes until confirmed
06COATING THICKNESS — WHERE THIS SITS IN THE STACK
Sealer / wet-on-wet
25-35 µm
THIS PRODUCT · GP1390 ▶
1-2 µm
FULL BUILD
81-132 µm of 300
Read it like the panel: substrate at the bottom, clear on top. Faded rows are the rest of the system at its normal build. See the Coating Thickness Guide.
MAXIMUM 2 µm (2.5 coats (1 light tack coat + 2 solid coats) at 1-2… — THE RED LINE ON THIS PRODUCT'S ROWPast that the film cannot get its solvent out: solvent pop, die-back, a soft film that never fully hardens, and cracking later. Modern polyurethane is a low-build system: less is better. Three thin coats do not fix what two correct coats did — they add microns and take the film past the limit. The red line on the FULL BUILD row is the 300 µm whole-panel ceiling — every layer added together.
07RECOAT & REWORK
| Recoat — this product over itself | TOPCOAT SAME DAY — apply basecoat or 2K colour once the primer is dry, within the same working day. Past the working day the window is closed: abrade lightly (P800-P1000 wet) and re-prime before coating. |
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HOW EACH COAT BONDS — WHY EVERY WINDOW ON THIS SHEET CLOSESThe whole repair is designed as
one system applied within one overall time frame: the primer is dried and sanded, but from colour onward it is a concurrent, same-day process — and every window on this sheet exists to keep you inside it. Within its window the next coat fuses chemically with the film beneath; past it, the film has cured and adhesion must be made mechanically — abrade, degrease, recoat. Heat closes windows sooner: cure runs on temperature, not the clock. Straying from the timed system — jobs interrupted, held over, stretched — is where the problems start. Full explanation in the
GERMA-TECH APPLICATION STANDARD.
If in doubt, abrade. IF YOU MISS THE RECOAT WINDOWOnce the film has cured past its recoat window, do not put another coat straight over it — the new coat sits on the surface and lets go at the interface. Abrade the whole area first (P800 wet or a grey abrasive pad), degrease, tack off, then recoat.
08PHYSICAL PROPERTIES
| Coverage | about 5.0-6.5 m²/L in practice (9.5 m²/L theoretical at 5 µm) Estimate, not a measurement. Indicative coverage at 5 µm dry film thickness, assuming 100% transfer efficiency. Real-world coverage is lower — spray guns lose material as overspray. Allow 55-65% of the theoretical figure. |
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| Density | approx. 1.15 (relative density, water = 1) — estimated from the Safety Data Sheet; not separately measured |
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| Gloss | N/A — not applicable to a primer |
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| Equipment cleaning | Clean guns and equipment immediately after use with gun wash or a solvent cleaner. Never let mixed 2K product start to cure in the gun — once it kicks, no solvent will save it. |
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09STORAGE, SHELF LIFE & PACKS
| Storage life (unopened) | Up to 36 months unopened — SUBJECT TO correct storage: a cool, dry place below 20 °C, out of direct sun. Heat is the biggest killer of paint in the tin: stock stored or transported in hot vehicles, tin sheds, shipping containers or direct sunlight loses life fast whatever the date on the tin, and that is where most premature failures start. Storage life is an optimal guide, not a promise that survives a hot shed. |
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| Once the seal is broken | Once the seal is broken the clock starts, and how you store it sets the pace. This product: 14 DAYS once the seal is broken, then discard.
All hardeners: 14 days once opened — then discard. Hardener is sealed without air; the moment air enters it starts to deteriorate. A part-used tin resealed tight lasts the 14 days; a loose lid does not. |
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| Storage | Store indoors in a cool, dry place below 20 °C, out of direct sunlight, with the lid sealed tight after every use. Never store or transport in heat — not in a tin shed, a shipping container, a hot van or a sunlit rack. |
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| Pack sizes | GP-1390 - 1lt |
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10PRODUCT CODES
| CODE | WHAT IT IS | PACK SIZE |
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| PC-1390 | Product | 1LT |
| GP5107 | Reducer · Premium Reducer | 20LT |
11WHERE IT SITS IN THE SYSTEM
BARESUBSTRATE
›
EPOXYPRIMER
›
FILLER
›
2K PRIMERSURFACER
›
SEALERWET-ON-WET
›
COLOUR
›
CLEAR
The highlighted step is where this product sits in the repair. Ancillaries support every step.
12STANDARD NOTES — THE SAME ON EVERY SHEET IN THIS SET
- Below 15 °C, air drying at ambient temperature is not recommended — allow a full bake at 60 °C metal temperature. SN1 · ALL BAKEABLE SPRAYED PRODUCTS
- At low humidity, a flash-off of 2-3 minutes between coats helps achieve a smooth film. SN3 · ALL SOLVENT-SPRAYED
- Above 30 °C ambient, add Retarder Solvent or move to the slow reducer to avoid blushing — refer to the Retarder Solvent TDS. SN4 · ALL SOLVENT-SPRAYED
- Fisheyes during application: add 0.5-1% Anti Silicon to the remaining paint and respray the affected area. SN6 · ALL SOLVENT-SPRAYED
- Total coating thickness on the panel — every layer together — must not exceed 300 µm. Refer to the Germa-Tech Coating Thickness Guide. SN7 · ALL FILM-BUILDING
- Do not dry in direct sunlight — panel temperatures in direct sun can exceed 70 °C. Allow 24 hours or a full bake. SN9 · ALL BAKEABLE SPRAYED PRODUCTS
- Germa-Tech products are designed to work as a system — fillers, primers, basecoat, clears, hardeners, reducers, abrasives and ancillaries — each graded and tested for compatibility with the products and processes on this sheet. Performance is only assured within the system, and a fault is only assessable within it: once non-Germa-Tech product has been used in the process, what touched the panel can no longer be verified. SN10 · ALL PRODUCTS
- *Flash-off times are measured at the stated temperature and MUST be adjusted for the day: colder than stated = LONGER flash, warmer = shorter. In winter, shops painting below 23 °C routinely under-flash — solvent is still in the film when the next coat lands. Below 15 °C, extended flash and air dry are not enough: bake the job. SN13 · ALL PRODUCTS WITH A FLASH-OFF
- 2.5 COATS means: start with a LIGHT TACK COAT, let it flash, then apply 2 solid coats — and STOP. Less is best. The tack coat sets adhesion and control; the two solid coats do the work. Extra coats add solvent load and film build, not quality. The tack coat and the 24-hour from-sanding rule are GT HOUSE RULES — taught and enforced here, deliberately tighter than published industry practice. The teaching behind this — Application Standard, section 03. SN14 · ALL 2.5-COAT PRODUCTS
Standard inclusions are controlled: each note applies to every product in its named set, enforced at build. They cannot drift onto some sheets and off others.
13PRODUCT-SPECIFIC NOTES
- 1. Apply basecoat or 2k colour directly to primer coat however do not apply wet on wet, primer must be dry
- 2. Can be sealed with 2k wet-on-wet primer if preferred
- Additional Care: Read safety data sheet before use. Product is highly flammable with a low flash point; container should be sealed (after use) and stored in cool dry and ventilated environment. Care must be taken to avoid static charge, electrical charges, flames or other conditions which may cause ignition. Wear rubber solvent proof gloves, eye protection and other appropriate PPE.
WARNINGS CARRIED FORWARD FROM THE PREVIOUS SHEETWARNING - some new plastic panels are pre-coated and primed with materials not suitable to be plastic primed. On the inside of new plastic panel (hidden side) apply a small amount of plastic primer and observe for adverse reactions. Do not apply too thick, 2.5 coats (1 light tack coat + 2 solid coats) at 1-2 µM is…
AMBIENT TEMPERATURE — WHY EVERY TIME ON THIS SHEET MOVESEvery time on this sheet — flash-off, drying, pot life, the recoat window — is quoted at 20-23 °C, and every one of them moves with temperature, because the two things that set them, solvent evaporation and chemical cure, are both driven by heat. As a working rule cure rate roughly doubles for every 10 °C rise: at 30 °C the times run at about half; at 15 °C they stretch to nearly half speed. Judge by panel temperature, not air temperature — a panel in sun or fresh out of the booth is far hotter than the shed.
HOT WEATHER (above 30 °C): everything shortens. Flash-off comes down, pot life comes down, and the recoat window closes early. Move to the SLOW hardener and slow or extra-slow reducer so the film has time to flow and release solvent — spraying standard speeds in heat is the fast road to dry spray and solvent boil.
COLD WEATHER (below 20 °C): everything stretches. Flash-off gets LONGER — the most common winter mistake is coating over a film that looks flashed but has not released its solvent, which traps it under the next coat and comes back as fry-up, dieback or runs. Move to the FAST hardener, and extend every flash. Below 15 °C standard 2K cure effectively stalls — bake the job, or wait for heat. Cold does not extend the recoat window in proportion either: contamination, moisture and flash rust run on the clock regardless of temperature.
14GOOD TO KNOW — WHAT WE GET CALLED ABOUT
- This grey one is not ready to spray - it must be reduced before application.
- 2.5 coats (tack + 2 solid) maximum, thin. Do not build it up.
- Let the primer dry before colour. No wet-on-wet over it.
- Wet sand P800-P1000, Prepsol, antistatic clean, then degrease again.
- Test a patch on the hidden side of new panels - pre-primed plastics can react.
15TROUBLESHOOTING
| DEFECT | WHAT YOU SEE | WHY IT HAPPENED | FIX |
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Adhesion failure on plastic | the finish lifts off a bumper, mirror or trim part in sheets, often peeling clean off the plastic with no key underneath | plastic primer missed or applied over a factory coating it cannot bond to, static and mould release left on the part, solvent cleaner used on bare plastic, or colour applied wet-on-wet over plastic primer | strip the affected part back, re-prep, re-test the primer on the hidden side and rebuild |
Lifting and wrinkling | the film shrivels, swells or folds into wrinkles while the new coat is going on or shortly after | solvent in the new coat attacking a sub-layer that is not solvent-proof - 1K primer or thermoplastic paint under a 2K coat, a coat put over an under-cured film, an over-long flash, or a coat put on outside its recoat window | let the affected area dry hard, sand the lifted film off down to a sound layer, prime past where the lifting stopped, and refinish |
Delamination and peeling | a coat lets go of the one under it - the film peels, flakes or lifts off cleanly in sheets, often starting at an edge or a stone chip | the surface underneath was not keyed or was not clean - missed degrease, wrong or no undercoat, sanding grit too fine or missed altogether, recoat window blown, or basecoat left too long before clear | remove all the loose film back to a sound layer, feather the edge, re-prime and rebuild the system properly |
Cracking and crazing | fine random cracks through the film, sometimes in a crows-foot pattern, worst over heavy build and over filler or flexible panels | total film build too high, too many coats stacked, plastic primer laid on too thick, a rigid film over a substrate that flexes, or a coat put over an under-cured layer | strip the cracked film back to a sound layer, re-prime and rebuild inside the film limits |
Dirt and dust inclusion | hard specks sitting in or under the cured film, felt with the back of the hand before they are seen | dust pulled in during application - panel not tacked off, static on plastic parts, dirty booth filters, contaminated air, overalls or gun, or crystallised additive poured straight from the tin | surface nibs come out after cure with P1500 working to P3000 then polish; anything embedded through the film has to be sanded and refinished |
AUSTRALIAN CONDITIONSAbove 30 °C ambient, move to the slow hardener and slow reducer and expect flash-off to shorten — dry spray and blushing are what a standard system gives you through a hot afternoon. Below 15 °C, air drying is not recommended: bake. In coastal and high-UV areas do not shortcut the epoxy step on bare metal.
16HEALTH & SAFETY
HEALTH & SAFETYFlammable solvent product. Use in a well-ventilated area away from ignition sources, with respiratory, eye, skin and hand protection selected in accordance with AS/NZS 1715 and AS/NZS 1716.
Read the Safety Data Sheet before use. REVISION HISTORY
| VERSION | DATE | CHANGE |
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| v2.3 | 02.09.2026 | Reissued on the current Germa-Tech technical data sheet format. New in this issue: a quick-reference card, the hardener and reducer selection gauge, the coating thickness stack, the recoat-window recovery procedure, and a product-specific troubleshooting table. Bake schedules are now stated as metal temperature. |
17WARRANTY & FURTHER INFORMATION
TALK TO US — WE MEAN ITWe are always happy to talk to customers who contact us directly. If anything on this sheet does not fit the job in front of you — an unusual substrate, a tight timeline, a cold morning, a window you have missed — call before you spray, not after.
support@amproaustralia.com · germatech.com.au This sheet is read together with the GERMA-TECH APPLICATION STANDARD (terms, conditions of application and warranty) and the Coating Thickness Guide — both hosted with the data sheets and at germatech.com.au. Warranty is conditional on correct use of the product as described on this sheet, including the sanding steps and grits in its sanding guide, within the Germa-Tech system. The information in this data sheet is given in good faith and is based on laboratory and field testing. Ampro Australia has no control over the conditions under which this product is used, so the end user must satisfy themselves that the product is suitable for the intended application and conditions. All times are quoted at 20 °C and 50% relative humidity unless stated otherwise. This sheet supersedes all previous issues.
