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Lash Adhesive / Cyanoacrylate

What’s the best lash glue?“ is the most asked question in lash groups. Understanding the most important 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 first start by explaining cyanoacrylate (CA for short). CA makes up ~80-95% of most lash adhesives so it gives lash glues most of its characteristics.

Cyanoacrylate

What is cyanoacrylate? How is it made? What’s the difference between cosmetic and medical-grade lash adhesives? Watch the video here:

Because of the reasons explained in the video I use medical grade cyanoacrylate when developing our adhesives.

What’s the difference between different types of acrylates?

The most common type of acrylates used in lash adhesives is cyanoacrylate due to its superior qualities over other types of acrylates. Around 2019 some polyacrylates lash adhesives were introduced to the lash world as hype to replace cyanoacrylate glues:

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

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

What’s the difference between different cyanoacrylate types?

  • Ethyl-cyanoacrylate. Currently the most popular type of cyanoacrylate in lash adhesives because it’s strong 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 – less fumes, less residue. It’s hard to get and not as resistant as ethyl- or methyl cyanoacrylate
  • Alkoxy-cyanoacrylate. Has the least fumes but is also the weakest one. It’s usually used in combination with other types of cyanoacrylate

What are lash glues made of?

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 colour.

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:

  1. 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
  2. Lash adhesives are made in a cascading effect. “Cascading effect” means that different ingredients are mixed together in steps, not all at once.

In order 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 and not the ingredients that were used in previous steps.

Here is a simple analogue with a cheese toast – when you make the toast you’d say that it is made of bread, butter and cheese. This is listing the final ingredients of a sandwich. Listing ingredients of the previous steps would be listing all ingredients 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 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 who used to add even more hydroquinone in step 2 stopped doing that. However, there are still some cheap lash glues available that have extra hydroquinone in step 2 added to them. Make sure that you don’t use a lash adhesive like that because it not only renders your insurance invalid (since you are using prohibited ingredients) but it means that the lash adhesive is of subpar quality. No respected manufacturer adds hydroquinone to their lash adhesives anymore.

  • PMMA – polymethyl methacrylate. Liquid plastic that makes cyanoacrylate stronger similarly to iron rods inside cement in buildings. 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 – used in 99.9% lash adhesives to colour them black. I do not use carbon black in our Dark Matter or PRO because some people are allergic to it. We use food colouring instead because the % of people who react to food colour is minute compared to carbon black allergy.

Less popular ingredients:

  • Silica – is a safer alternative to PMMA for the same purpose. We use Silica in our Dark Matter and PRO instead of PMMA.
  • Latex – used to be used as an alternative to PMMA for the same purpose

Bad marketing tactics used for lash glues

  • “Formaldehyde-free”. ALL lash adhesives are formaldehyde-free! Formaldehyde forms as a by-product when lash 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” There is a big difference between whether something is oil-proof or 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 over a long period of time. Oil-resistant simply means that it will not break down as soon as it becomes 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 oilproof, then customers with oily skin would not have worse retention than customers with regular skin. Out of our adhesives, Dark Matter & PRO are oil proof and Universal Bond & Elite Bond Adhesive are oil resistant.
  • “double or triple purified” implying that other adhesives are purified fewer times. Distillation is a purification process by 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

How does lash adhesive work?

Curing

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, tougher 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 that as soon as you dispense a glue dot, the polymerization will begin. Air humidity will start curing your glue dot of its outer layer and work its way in, which means that the glue dot is always freshest in its centre.

1. Cyanoacrylate is kept liquid by the presence of a stabilizer (usual hydroquinone). Stabilizer molecules block cyanoacrylate monomers from joining.
2. When hydrogen molecules (H2) are introduced, they attract and join with stabilizer molecules and thus neutralize them. Cyanoacrylate monomers can start joining to form a long chain polymer = polymerization.
3. All stabilizer molecules are neutralized = cyanoacrylate is fully polymerized

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

How is curing speed calculated?

Lash adhesives’ curing speed (that’s 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 from the moment you dip lashes into the glue. This means that if you are working with a 1-second glue, you have 1 second to adjust its placement on the natural lash, until moving it will be very difficult and affect retention. This is if you are working in the correct environment for that adhesive.

Watch this video for further explanation:

How long does cyanoacrylate take to cure?

Different types of cyanoacrylate take different times to cure. 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 it has fully cured so I don’t recommend washing your customers’ lashes post-treatment without using Superbonder first. This can affect retention in a negative way! It won’t make all eyelashes fall off but it will weaken the glue bond enough to have an impact on the average retention your customers are experiencing.

How can I tell how fast my adhesive is curing?

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

I think learning how to do this should be one of the first things any new lash artist learns 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 change in colour 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:

Shock polymerization (blooming)

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 recognised by CA turning white. This happens usually:

  • If room humidity is too high
  • If lashes are too wet (from the preparation stage or watery eyes during the treatment)
  • Nano mister 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 important to first recognise it and then remove the reason that’s causing your lash adhesive to shock polymerize!

-Ruthie Belle Ultimate Guide

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