PRIMER / UNDERCOAT · THE FOUNDATION
1K PRIMER SURFACER
GP3501
Germa-Tech 1K Primer Surfacer is a Hi-build 1k primer - fast drying single pack primer surfacer, suitable to cover minor defects and pin holes. Easy to apply with good filling properties…
SCAN FOR THE FULL RANGE,
APPLICATION GUIDES & VIDEOS
germatech.com.au
TDS v2.3 · ISSUE 02.09.2026
SUPERSEDES 07.2022
REVIEW DUE 07.2028
1 : 0.8 -1 (80% - 100%)
BY VOLUME
GRAVITY 1.4-1.8 mm · SUCTION 1.7-2.0 mm
HVLP 2.0 bar · RP 2.0-2.5 bar · CONV 3-4 bar
2.5 coats (1 light tack coat + 2 solid coats)
At 20 °C, 5-10 minutes*
*ADJUST FOR THE DAY'S TEMPERATURE
01SUITABLE SUBSTRATES
- Dried and sanded existing finishes and putty.
02SURFACE PREPARATION
Remove Wax, Silicon and other contaminants with Germa-Tech Prepsol
03MIXING
| PRIMER | REDUCER |
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| GP3501/GP3504 | Germa-Tech Premium Reducer |
| Ratio by volume | 1 : 0.8 -1 (80% - 100%) |
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| Ratio by weight | 1 : 0.8 -1 (80% - 100%) |
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| Notes | The sheet gives a single Weight/Volume row of 1 : 0.8-1 (80%-100%) thinner. |
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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 | 1.4-1.8 mm |
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| Gun — suction feed | 1.7-2.0 mm |
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| Pressure — HVLP | 2.0 bar |
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| Pressure — RP | 2.0-2.5 bar |
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| Pressure — conventional | 3-4 bar |
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| Coats | 2.5 coats (1 light tack coat + 2 solid coats) |
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| Flash-off between coats | At 20 °C, 5-10 minutes |
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| Dry film build | 40-60 µm total |
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05DRYING & CURING
| TEMPERATURE | DRY |
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| 20 °C | 45 minutes |
06COATING THICKNESS — WHERE THIS SITS IN THE STACK
Sealer / wet-on-wet
25-35 µm
THIS PRODUCT · GP3501 ▶
40-60 µm total
Body filler
shaped back — not film
SUBSTRATE
bare steel / prepared panel
FULL BUILD
160-250 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.
07RECOAT & REWORK
| Recoat — this product over itself | TOPCOAT: THIS SURFACER IS ALWAYS SANDED BEFORE COLOUR — there is no un-sanded route to topcoat. Sand to the finish grade (P500-P600 dry or P800 wet; P800 for metallic and pearl colours), then the 24-hour from-sanding window applies. |
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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.
08SANDING GUIDE — STEPS, GRITS & ABRASIVES
| Step | Grit | What you are doing | Germa-Tech abrasives — examples by part number |
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| 1 · Guide coat | — | Dust a contrasting guide coat over the dry primer. It sits in every low spot and scratch — when the guide coat is gone, the panel is flat and proven. | guide coat aerosol/powder |
| 2 · Cut & level | P400 dry | Block or DA the primer level. The guide coat shows exactly where you are. | ORBIT GOLD 150 mm P400 (M6-P400-100) · VIBE long block 115×225 P400 (GSR115400) · BLOCK CERAMIC 70×125 P400 (GSR125400) |
| 3 · Finish for colour | P500–P600 dry (or P800 wet) | Refine the P400 scratch ready for basecoat. Under a direct-gloss 2K colour P400–P500 is enough; under basecoat finish P500–P600. | ORBIT GOLD 150 mm P500 (M6-P500-100) · P600 (M6-P600-100) · SHEER ROLL FOAM 115 P600 (GFR600) for hand work |
| 4 · Feather the edges | P600–P800 | Feather every primer edge into the old finish until you cannot feel it with a bare hand. | ORBIT GOLD 150 mm P800 (M6-P800-100) · SHEER ROLL FOAM 115 P800 (GFR800) |
AFTER SANDING — THE CLOCK STARTSDegrease, tack rag (PB013), and get colour on within 24 hours of sanding — the from-sanding window on this sheet is contamination-limited and does not stretch in cold weather. Leave it longer and the panel needs a re-scuff.
LARGE JOBS — WHEN SANDING TAKES MORE THAN A DAY: on bigger jobs the panels sanded first can be outside the 24-hour window before the last panel is finished. Give the whole job a light scotch rub immediately before colour goes on, and a coat of wet-on-wet primer (GP3201 System 1) is also advised — it seals off any imperfections and puts a fresh, uniform surface under the colour.
THE 100-GRIT RULE — WHY THE SEQUENCE MATTERSEach grit exists to remove the scratches left by the one before it. Never jump more than about 100 grit in one step — a P80 scratch will not come out with P400; it gets buried, then telegraphs through the topcoat weeks later as sanding-mark showthrough. Work the sequence, prove the panel with a guide coat, and step down evenly.
THESE STEPS ARE A WARRANTY CONDITIONFollowing the steps and grits above — with
Germa-Tech abrasives — is a condition of product warranty, not a suggestion. P-grades are only comparable within a controlled range: a recent claim traced to an ungraded brand’s “P320” that cut like a true P240, leaving scratch in the primer that showed through the finished clear. The part numbers above are graded and tested for compatibility with this product and this process — which is what makes a fault assessable: once non-Germa-Tech product has been used, what touched the panel can no longer be verified, and issues arising cannot be fairly assessed. Refer to the
GERMA-TECH APPLICATION STANDARD.
09PHYSICAL PROPERTIES
| Coverage | about 2.8-3.3 m²/L in practice (5.0 m²/L theoretical at 50 µm) Estimate, not a measurement. Indicative coverage at 50 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. 1.20 (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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10STORAGE, 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 | GP3501: 4kg*4 cans per box · GP3504: 1lt*12 cans per box |
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11PRODUCT CODES
| CODE | WHAT IT IS | PACK SIZE |
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| GP3501 | Product | 4LT |
| GP3504 | Product | 1LT |
Stated on the source sheet without a code: Reducer: Germa-Tech Premium Reducer
12WHERE 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.
13STANDARD 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
- FINISH FOR COLOUR — THE STANDARD GRADE. The last sanding pass before colour is P500-P600 dry (or P800 wet). METALLIC AND PEARL COLOURS REQUIRE P800, dry or wet — coarser scratches telegraph through the flake and show in the finish. Any coarser grits on this sheet are shaping or stripping stages, not the finish. SN16 · FINISH FOR COLOUR
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.
14PRODUCT-SPECIFIC NOTES
- 1. Not recommended for direct application over substrates of bare metal and wood
- 2. Recommended to use 2K Primer to achieve good adhesion to substrates and excellent gloss and film build of the topcoat.
- 3. It is not recommended to use a fast drying thinner.
WARNINGS CARRIED FORWARD FROM THE PREVIOUS SHEETMust be reduced with Germatech Reducer
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.
15GOOD TO KNOW — WHAT WE GET CALLED ABOUT
- Not for bare metal or timber. It goes over dried, sanded existing finishes and putty only.
- It must be reduced with Germa-Tech Reducer.
- Do not use a fast drying thinner in it.
- Where you need real adhesion and topcoat gloss holdout, use the 2K primer instead.
16TROUBLESHOOTING
| DEFECT | WHAT YOU SEE | WHY IT HAPPENED | FIX |
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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 |
Shrinkage over filler | the repair looks flat when it leaves the booth and the filler shape shows back through days later, usually as a dull low patch | filler or primer sanded before it had cured through, over-hardened filler, filler applied too thick in one hit, or primer stacked past its coat limit | sand the sunken area back, re-prime with 2K hi-fill, let it cure properly, block flat and refinish |
Sanding-mark showthrough | the sanding scratch pattern from the stage underneath telegraphs through the finished film, often as fine parallel lines or DA swirls | grit too coarse for the coat going over it, the undercoat not fully cured before it was sanded, or the finish grit skipped so a coarse scratch was never removed | sand the area back flat at the correct finishing grit, re-prime, and refinish |
Edge mapping and ringing | a visible ring or outline of the repair showing through the finished panel, following the featheredge or the primer patch | primer sanded too thin at the featheredge so topcoat solvent reaches the old finish, featheredge grit too coarse, or the primer not fully cured before topcoating | sand the ring back, re-prime over the featheredge with 2K primer, let it cure, and refinish |
Rust breakthrough | rust staining or blistering pushing up through the finish, usually along a repair edge, a weld, a stone chip or a panel bottom | bare or rusted metal coated without proper treatment, filler or surfacer put straight on bare steel and left, oxidation forming between prep and priming, or a coating not cured hard enough to seal | cut the corrosion out back to sound clean metal, epoxy prime, then rebuild the system |
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.
17HEALTH & 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 |
|---|
| 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. |
18WARRANTY & 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.
