Lash Adhesive / Cyanoacrylate

„What’s the best lash glue?“ is the most asked question in lash groups. Understanding the essential chemical in lash artists’ lives – cyanoacrylate – will enable you to get the best retention out of any lash adhesive so that you never have to ask that question yourself!

To explain lash adhesives, I must explain cyanoacrylate (CA for short). CA makes up ~80-95% of most lash adhesives, giving lash glues most of its characteristics.

The most common type of acrylate used in lash adhesives is cyanoacrylate, which is superior to other acrylates. However, around 2019 some polyacrylate lash adhesives were introduced to the lash world as a hype to replace cyanoacrylate glues:

Polyacrylates are more toxic than cyanoacrylate and should not be used in lash adhesive.

Multiple different types of cyanoacrylates may be used for making lash extension adhesive. They all have slightly different characteristics in their curing speed, viscosity flexibility (elasticity), durability, breakage resistance, and oil resistance.

• Ethyl-cyanoacrylate. Currently, the most popular type of cyanoacrylate in lash adhesives because it’s solid and  elastic at the same time
• Methyl-cyanoacrylate. Used to be the most popular cyanoacrylate when modern lash extensions became popular 
• Butyl-cyanoacrylate. The cheapest and lowest grade 
• Octyl-cyanoacrylate. Used by surgeons – fewer fumes, less residue. It’s hard to get and not as resistant as ethyl- or methyl cyanoacrylate
• Alcoxy-cyanoacrylate. It has minor fumes but is also the weakest one. It’s usually used in combination with other types of cyanoacrylate.

Cyanoacrylate makes up the majority of lash adhesives by far. However, other ingredients are also used to keep the lash glue from polymerizing inside the bottle to give it elasticity and black color.

Most popular ingredients:

• Hydroquinone – stabilizer that keeps lash glue from polymerizing inside the bottle.

PRO TIP: Using hydroquinone in cosmetic products was prohibited in the European Union in 2020. 

So many lash artists have started focusing on this matter since then. There are a few things to note about this matter, though:

• Lash adhesives are no longer considered cosmetic products in the European Union. They are now considered to be chemicals, so this regulation does not apply to them.
• Lash adhesives are made with a cascading effect. “Cascading effect” means that different ingredients are mixed in steps, not all at once.

To make lash adhesive, you must first have or make cyanoacrylate (step 1). Step 2 is mixing CA with other ingredients such as PMMA, carbon black, etc. Cosmetic regulation requires listing only the ingredients used in the final step of making any product, not those used in previous steps.

Here is a simple analog with cheese toast – when you make the toast, you’d say it is made of bread, butter, and cheese. This lists the final ingredients of a sandwich. Listing ingredients of the previous steps would be listing all components that were used to make the bread, all ingredients that were used to make the butter, and all ingredients that were used to make the cheese.

Hydroquinone is added to cyanoacrylate in step 1 when raw cyanoacrylate is made from the cyano acrylic acid. Some companies added it to the ingredients list because it’s a harsh chemical, so when the ban came, they simply stopped listing it because, by law, they were not required to. This does not mean that there exist any hydroquinone-free lash adhesives! The only thing this regulation changed is that most lash companies that used to add even more hydroquinone in step 2 stopped doing that. However, some cheap lash glues are still available, with extra hydroquinone in step 2 added to them. Make sure you don’t use a lash adhesive like that because it renders your insurance invalid (since you are using prohibited ingredients) and means that the lash adhesive is of subpar quality. No respected manufacturer adds hydroquinone to their lash adhesives anymore.

• PMMA – polymethyl methacrylate. Liquid plastic makes cyanoacrylate stronger, similar to iron rods inside building cement. Without PMMA, cyanoacrylate would be strong like cement but more brittle, just like cement buildings would not stand up without the help of the iron rods.
• Carbon black is used in 99.9% of lash adhesives to color them black. 

Less popular ingredients:

• Silica – a safer alternative to PMMA.
• Latex – used to be used as an alternative to PMMA.

• “Formaldehyde-free.” ALL lash adhesives are formaldehyde free! Formaldehyde forms a by-product when eyelash glue cures; it is not an added ingredient in ANY lash adhesive. On top of that, formaldehyde is far from being as dangerous as some fear mongers have made it out to be – even humans produce some formaldehyde with breathing!
• “waterproof.” ALL lash adhesives are waterproof! If they weren’t, then lash extensions would fall off as soon as you wash your face.
• “oil resistant” is a big difference between oil-proof and oil resistant. Oil-proof means that it will not break down in the extended presence of oil and that it is not sensitive to oil even after being exposed to it for a long time. Oil resistance means that it will not break down as soon as it comes into contact with oil, NOT that it will not break down at all. ALL lash adhesives are oil resistant. Not all lash glues are oil-proof, though! If all lash adhesives were oil-proof, then customers with oily skin would not have worse retention than customers with regular skin. 
• “double or triple purified,” implying that other adhesives are purified fewer times. Distillation is a purification process through separating a compound from a non-volatile or less volatile material. Raw cyanoacrylate is made by distilling cyano acrylic acid many, many more times than just twice or three times. Purifying cyano acrylic acid twice or three times gives you industrial grade cyanoacrylate, which is a lower quality that’s required for lash adhesives

Lash adhesives glue extensions to natural lashes by curing. Curing is a process during which a chemical reaction (such as polymerization) or physical action (such as evaporation) takes place, resulting in a harder, more rigid, or more stable linkage (such as an adhesive bond).

Curing starts as soon as lash adhesive comes into contact with air (water molecules in the air, to be more precise). This means the polymerization will begin as soon as you dispense a glue dot. Air humidity will start curing your glue dot from its outer layer and work its way in, meaning it is always freshest in its center.

Since cyanoacrylate needs the presence of humidity (hydrogen) to cure correctly, it’s important NOT to strip natural lashes from all moisture!

Lash adhesives’ curing speed (usually mentioned in the product description and on the glue bottles) is calculated from the point of contact, i.e., when extensions touch the natural lashes, NOT when you dip lashes into the glue. If you work with a 1-second glue, you have 1 second to adjust its placement on the natural lash. Moving it will be challenging and affect retention. This is if you are working in the right environment for that adhesive.

Watch this video for further explanation:

Different types of cyanoacrylate take different times to cure. However, since ethyl-cyanoacrylate is the most popular type used in lash adhesives, I'll focus on that.

90% of ethyl-cyanoacrylate cures in about 2 minutes. The remaining 10% can take up to 24h to cure. If you use our Superbonder after the 2 minutes, you'll speed the curing process so much that the remaining 10% will cure in just 3 minutes! Do not apply Superbonder sooner than 2 minutes after applying the last extension, though, because that first 90% needs to cure by itself, uninterrupted. Cyanoacrylate will only become water-resistant after fully cured, so I don't recommend washing your customers' lashes post-treatment without using Superbonder first. This can negatively affect retention! It won't make all eyelashes fall off but will weaken the glue bond enough to impact the average retention your customers are experiencing.

Learning to tell when the adhesive has cured visually is severely underrated in our industry. Applying extensions with semi-cured glue (when it cures faster than you can place them on the natural lash) is a highway to lousy retention.

Learning how to do this should be one of the first things any new lash artist knows if they want to achieve good retention! So here’s the trick: when the lash adhesive is wet (not cured), it’s shiny black. When it cures, it will become dull black. This is it! Learn how to notice the color change, and soon, your eyes will detect it without even thinking about it!

Here is a video demonstrating how the glue changes from shiny to dull when it’s curing:

When too much moisture or undesirable chemicals are introduced to cyanoacrylate, it will cause the CA to polymerize too fast. This results in a weaker bond and can be recognized by CA turning white. This usually happens:

• If room humidity is too high
• If lashes are too wet (from the preparation stage or watery eyes during the treatment)
• Nanomister is used too close.
• You have undesirable chemicals in your working area (for example, hair stylists or lash lift artists – ammonia is the most popular ingredient that has this impact on lash adhesive)

Blooming NEVER provides good retention, so it’s essential first to recognize it and then remove the reason causing your lash adhesive to shock polymerize!

This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.