What Is Amine Blush?

Amine blush is a waxy, or greasy (sometimes slightly sticky) layer that sometimes appears on the surface of curing or fully cured epoxy resin. It forms when the amine hardener reacts with moisture and carbon dioxide in the air. This usually happens when the humidity is too high, temperatures are low, or other environmental conditions are not ideal.

Other Names for Amine Blush (locally known as): Meeduma (මීදුම), Thel Palama (තෙල් පලම), Clouds or haziness, Sticky residue or waxy film, Surface blush or contamination.

Note: This article is based on epoxy products available in Sri Lanka. Many popular international brands are not widely available locally. The information here is based on our own testing, experience, online resources, and customer feedback over the years.

How to Identify Amine Blush You may have amine blush if:

• Waxy, greasy or slightly sticky surface: Even after curing, the surface may feel slightly tacky or oily. This usually means blush, not just incomplete curing.
• Cloudy patches or hazy appearance: Instead of a clear, glossy finish, the surface may look dull or milky in certain areas.
• Poor bonding with the next resin layer: A second pour may peel, bubble, or not stick well due to the blush acting as a barrier.
• White or patchy spots when sanding: Sanding a blushed surface often reveals chalky or uneven patches and may clog your sandpaper.
• Paint or varnish won’t stick properly: Topcoats like paint or varnish may streak, peel, or fail to bond if applied over an uncleaned blush layer.

What Causes Amine Blush?

Amine blush is primarily caused by environmental factors that allow moisture to interact with the curing epoxy. Here are the key reasons:

1. High Humidity: This is the most common cause. When the humidity level is high, excess moisture in the air reacts with the amine component in the hardener. This chemical reaction forms a thin, greasy or waxy layer on the surface known as amine blush. In tropical countries like Sri Lanka, this is especially common during rainy or monsoon seasons.
2. Cool Temperatures: Cold weather slows down the curing process, which means the resin stays in its reactive (uncured) state for a longer time. The longer the resin is exposed to open air, the more time it has to absorb moisture especially if humidity is high. This extended exposure increases the risk of amine blush.
3. Poor Air Circulation: Good ventilation is essential when working with epoxy resin. Fresh air should ideally flow from one side of the workspace and exit from the other. Without proper airflow, humidity builds up indoors, especially in closed rooms. A buildup of moisture-rich air increases the chances of blush forming. In addition, stagnant air can trap toxic fumes, making the workspace unsafe. Using an exhaust fan or cross-ventilation setup helps control both humidity and air quality.
4. Incorrect Resin to Hardener Ratio: If you don't mix the resin and hardener in the correct ratio, the chemical reaction becomes unbalanced. This can slow/fast curing, leave unreacted amines on the surface, and increase the likelihood of amine blush forming especially when exposed to humid air.
5. Slow-Curing Epoxy Systems: Epoxies with a long pot life or open time are more prone to blush because they remain uncured for longer. This gives more opportunity for moisture in the air to react with the surface. These types of resin are often used for large pours or deep castings, where the risk of blush is higher if the environment is not well controlled.
6. Pigments, Alcohol Sprays & Moisture Containing Additives:
   Using water-based pigments, dyes, or powders can introduce moisture into your epoxy mix. Even small amounts can cause amine blush, cloudy finishes, or poor curing.
   Alcohol sprays to remove bubble can also be a problem. Many common alcohols like surgical spirit, rubbing alcohol, or sanitizer sprays contain water. This moisture can react with the resin surface during curing.
   To prevent this:

• • Use only dry pigments or resin-safe colorants. Moisture from pigments or sprays is a common but avoidable cause of amine blush in resin work.
  • Use a bubble remove spray epecially made to remove bubbles on resin, or If using alcohol spray, make sure it’s water-free (99% isopropyl alcohol).

Misconceptions About Amine Blush & Open Flame

Some believe that using a gas lighter or blow torch causes amine blush or can remove it. Both are incorrect.

❌ Open flames do not cause amine blush: Amine blush forms when the amine hardener reacts with moisture in the air, not because of heat or flame.

❌ A flame cannot remove amine blush: You may evaporate surface moisture temporarily, but the waxy film remains. In some cases, heat can even worsen the problem.

In rare cases, the carbon dioxide released from a flame (like a gas lighter or torch) may slightly increase the local CO₂ level around the curing resin. Since CO₂ is part of the reaction that causes amine blush (along with moisture), this could, in theory, raise the risk slightly.

However, at the same time, the heat from the flame can warm the surrounding air, reducing humidity which helps prevent blush. So while the effect of CO₂ is real, it’s minor and usually balanced out by the reduced moisture from the heat. In practice, the overall impact is minimal and not enough to say that flame causes or prevents blush.

Why Doesn’t Amine Blush Happen Every Time? Amine blush is more likely when humidity is high, but dew point also plays a role. The dew point is the temperature at which moisture in the air starts to condense. If your resin surface or workspace is close to this temperature, moisture can settle on the resin and react with the hardener, causing blush. This often happens at night or in poorly ventilated areas where temperatures drop and moisture builds up.

Which Epoxies Are More Likely to Blush?

Epoxies That DO Get Amine Blush

• These typically use traditional or unmodified amine hardeners.
• Regular Amine-Based Hardeners
• These include polyamines, aliphatic amines, and polyamidoamines.
• Common in marine grade, construction, or general purpose epoxy resins.
• These are highly reactive with moisture (H₂O) and carbon dioxide (CO₂), forming a water-soluble surface film i.e., amine blush.
• Slow Curing Formulations
• Longer curing times = more time for moisture to interact.
• Blush often appears when cure happens overnight in cool or humid environments.
• High Humidity Cure Conditions
• Even blush resistant formulas can blush in very humid climates if conditions are poor (common in Sri Lanka).

Epoxies That Rarely or Never Blush

These use specially modified hardeners or alternative chemistries designed to resist or eliminate surface reactions.

• Cycloaliphatic Amines (Non-Blushing)
• These are more stable and less sensitive to moisture and CO₂.
• Often used in high-performance coatings and UV-resistant systems.
• Modified Amine Hardeners (Low-Blush or No-Blush)
• These are chemically altered to reduce surface reactivity.
• Often used in art resin, doming resin, or casting resin.
• Fast-Curing Epoxies
• Fast cure means less exposure time to humidity during curing.
• Solvent-Based Epoxies
• Solvent presence can reduce surface moisture effects.
• Not common for crafts or art due to fumes.

Misconceptions About Amine Blush

Some sellers and users wrongly believe that blush indicates low-quality resin. In truth, it’s a natural chemical reaction. Traditional industrial-grade epoxies are more prone to it due to their formulation not because they’re poor in quality.
Art grade resins are specially modified to prevent blush, but that doesn’t make other epoxy systems inferior. Marine grade or construction resins are highly durable but more reactive with moisture. Amine blush doesn’t mean the resin is bad it just means that it's most likely a industrial grade resin.

Tropical Climate & Amine Blush: Why It Matters in Sri Lanka

High humidity and temperature changes in Sri Lanka increase the chance of amine blush, especially:

• When resin cures overnight in humid conditions
• When there’s poor airflow or ventilation
• During rainy or monsoon seasons

Even blush resistant epoxies can develop blush in extreme conditions. Always cure in a dry, ventilated space. Use fans or a dehumidifier if necessary.

How to Know If an Epoxy Resin Will Get Amine Blush

Epoxy resin labels don’t always mention amine blush, but you can often guess based on a few clues:

• First, simply ask the seller if this epoxy resin is prone to amine blush in humid or moist conditions.
• When in doubt do a small test pour if the cured surface feels sticky or waxy, it’s likely prone to blush.
• If the resin uses traditional amine hardeners (like aliphatic or polyamines), it's more likely to blush.
• Resins made for art, doming, or jewelry often use modified or cycloaliphatic hardeners and are usually blush resistant.
• Slow-curing or cold-weather formulas have more time to react with humidity, increasing the chance of blush.
• If the product description says "non-blushing" or "no surface prep before recoating," it’s a good sign.

How to Avoid Amine Blush

Control Environment:

• Work in low humidity conditions (ideally under 70%, the lower the better).
• Maintain temperatures between 22–28°C (71–82°F) when curing.
• Avoid working during rainy, misty, or very humid days if you're not in a climate-controlled room.

Choose the Right Resin:

• Use non-blushing or blush-resistant epoxy systems, especially those designed for art/casting.

Use Accurate Mixing Ratios:

• Measure by volume or weight accurately, based on manufacturer's instructions.
• Mix thoroughly to prevent soft or undercured areas.

Improve Air Circulation:

• Make sure your workspace has good airflow to prevent humidity from building up. Use cross-ventilation or install an exhaust fan to help remove moist air and resin fumes.
• Avoid covering pieces tightly during cure (unless using a dry box or chamber).

Keep Surface Clean:

• Don’t touch the curing surface, finger oils can trap moisture.
• Avoid spraying water, mist, or alcohol (less than 99%) on the curing surface.

Apply Heat Carefully:

• If using heat guns or torches, avoid overheating, which can draw moisture to the surface.

Heat Source Near Curing Resin Piece:

• Using a small heat source, such as a low-heat 25-40W filament bulb, near your curing resin piece can help maintain a stable temperature and reduce moisture in the air. This can be useful in preventing amine blush, especially in cool or humid conditions. However, this method isn't suitable for all situations, avoid using it for large pours or with high-wattage heat sources, as it may cause overheating or uneven curing.

What Happens If You Don’t Remove Amine Blush?

If you don’t clean off amine blush, the surface may stay cloudy or sticky. New resin layers, paint, or varnish won’t bond properly, and the sticky finish can attract dust and hair. Skipping this step can affect both the look and strength of your project.

How to Remove Amine Blush

You can find full Step-by-Step guide here: How to remove amine blush (Coming Soon)

Amine blush must be fully removed before sanding, repainting, or pouring a new resin layer. Here’s how to do it the right way:

Step 1 Spotting Blush During Early Cure (Optional): Sometimes, during the early gel stage, you may see small waxy or greasy patches forming. These can occasionally be remove with a toothpick, but this is rare and not reliable for most cases.

Step 2 Wash the Surface Thoroughly: Once the resin is fully cured (check manufacturer's label for curing times), wash the surface, especially if there's only a thin blush layer:

• Use warm water and mild dish soap
• Gently scrub with a non-abrasive sponge or pad
• Rinse well and let it dry completely

⚠️ Never sand before washing. Doing so may push the blush deeper into the surface and cause adhesion problems later.

Step 3 Optional: Wipe with Vinegar or Alcohol:

• If the surface still feels greasy or shows signs of blush after washing:
• Wipe gently with white vinegar or 99% isopropyl alcohol
• Do not use acetone or harsh solvents, they can damage the resin or spread the blush

Step 4 Sand Only After Cleaning, Once clean and dry:

• Lightly sand the surface if needed
• Use 320–600 grit sandpaper depending on your project
• Remove any dust before recoating

Step 5 Recoat or Finish, Now the surface is ready:

• Pour a new resin layer
• Or topcoat

Properly removing amine blush helps ensure strong bonding and a clean, professional looking finish.

Amine blush is a common issue, especially in humid places like Sri Lanka. But with the right resin, good curing conditions, and proper prep, it’s easy to avoid or remove.

Knowing how to spot, clean, and prevent blush ensures professional, long-lasting results for your resin projects, whether you're making art or building something tough.