10.2 Physical Change, Chemical Change, and Polymerization

10.2 Physical Change, Chemical Change, and Polymerization

NIC Domain 3 tests chemical interactions, physical changes, and chemical reactions, not just ingredient names. If you cannot tell a Spokane client why polish dries but acrylic sets, you will miss items and you will troubleshoot the wrong way at the table. Washington then expects you to store and mix those chemicals so they do not injure a client, but the chemistry question is simpler than a brand catalog: did a new substance form, or did the same substance change form?

Physical change: same substance, different form

A physical change rearranges or removes material without creating a new chemical substance. The molecules that remain are the same kind of molecules.

Evaporation of solvent in polish is the textbook physical change on a manicure table. Wet lacquer is film former, plasticizer, pigment, and solvent together. As acetone, ethyl acetate, or other solvents leave the film, the nitrocellulose-type film former remains as a coat. You did not polymerize a new plastic in the lamp-and-initiator sense. You waited for solvent to leave. That is why air-dry polish can skin over in a breeze and why a thick coat stays soft in the middle: solvent is trapped, not uncured photoinitiator. Fanning polish is still evaporation. A UV lamp pointed at regular lacquer is not a chemical cure unless that product was actually a gel system with photoinitiators.

Soaking off is also largely physical. Acetone or another specified solvent dissolves or swells polish film, wrap resin, many acrylics, and many soft gels so you can gently remove them. You are not cooking a new polymer. You are using a solvent to reverse a physical film or to break up a polymer network enough to slide it off. Forcing product with a bit until you hit the bed is not faster chemistry. It is injury. WAC 308-20-110(1)(e) still bars continuing on open or inflamed tissue if you create a wound while prying.

Filing is mechanical reduction. An e-file or hand file removes particles of already-formed product or keratin. No new substance appears. Dust is still polymer or keratin, just smaller. That is why dust control from Chapter 6 is still the same material, now airborne. Shaping a tip before glue, buffing a dehydrated plate, and wiping polish with remover are physical operations. They matter for adhesion. They are not polymerization.

Chemical change: a new substance forms

A chemical change (chemical reaction) produces new substances with different properties. On a nail table, the reaction you must be able to name is polymerization.

Polymerization is the linking of small monomer molecules into long polymer chains. The liquid or gel you applied is not the same material as the hard overlay you send out the door. Heat, a change from glossy wet to solid, and a product that will no longer dissolve the way the liquid did are clues a reaction occurred.

Three polymerization stories dominate NIC chemistry:

1. Acrylic liquid and powder. EMA monomer wets polymer powder. Benzoyl peroxide in the powder initiates chain growth. The bead goes from a glossy mix to a solid enhancement. That solid is a new polymer network around the powder beads, not dried water. Air does not replace the initiator. A fan does not replace mix ratio.

2. UV/LED gel cure. Photoinitiators absorb the lamp's energy and start acrylate or methacrylate polymerization. No correct light, no chemical finish. A gel that sits on the table under a Tacoma ceiling fixture is not curing slowly like polish. Thickness matters because light has to reach the photoinitiator throughout the layer. A glob that is opaque at the center can stay chemically undercured even if the surface looks set.

3. Cyanoacrylate polymerization. Nail glue, wrap resin, and many dip resins set when the cyanoacrylate meets moisture. The polymer forms in seconds. That is why glue grabs a tip, why it can bond skin, and why a sealed bottle still skins over if humidity and leftover product sit in the nozzle. You cannot undo that reaction with the same shrug you use for wet polish. Soaking may swell or weaken some cyanoacrylate films later; the set itself was still a chemical change.

If the exam stem says a new, harder substance formed after liquid met powder, after gel met the lamp, or after glue met moisture, you are in chemical-change territory.

Mix ratio: wet beads, dry beads, and the working bead

Acrylic polymerization is ratio-sensitive. Mix ratio is how much monomer liquid wets how much polymer powder.

A medium working bead — the classic trained bead — is glossy enough to move but not so wet that it floods the eponychium. The initiator in the powder and the monomer in the liquid are in a range the manufacturer designed. The set time is predictable. The cured polymer has both adhesion to a prepared plate and cohesion inside the overlay.

A wet bead is liquid-heavy. Too much monomer, not enough powder and initiator relative to that liquid. The mix can run into living skin, set slowly, stay gummy, shrink, or form a weak overlay that lifts. Technicians sometimes chase a wet bead with more wait time instead of correcting the ratio. Extra lamp time will not fix acrylic because acrylic is not a photoinitiator system.

A dry bead is powder-heavy. Too little monomer to wet the polymer. The mix looks dull or crumbly, does not self-level, and cures into a brittle, poorly adhesive lump. Dry product does not grab harder. It starves the reaction of the liquid that must surround the beads. Filing a dry, brittle overlay into shape is still a physical change performed on a chemically weak polymer.

There is no WAC 308-20 numbered bead-wetness rule. There is manufacturer chemistry. NIC will still expect you to know that ratio changes the polymer you get. In a Federal Way booth, dipping the same brush into a contaminated dappen all day also changes the ratio because leftover polymerized crumbs steal liquid.

Oxygen inhibition layer on some gels

Some gels, especially some traditional UV formulations, leave a tacky surface after the lamp because oxygen at the air interface inhibits complete surface polymerization. That sticky film is the oxygen inhibition layer. It is a known surface phenomenon, not proof that the entire enhancement is raw.

Manufacturer instructions may tell you to wipe it with a specified cleanser, often an alcohol-type wipe, after cure, or they may sell no-wipe top coats formulated to reduce that layer. Wiping is not optional improvisation with dish soap. Do not file a sticky inhibition layer as if it were dust and then complain the shine died — you may be grinding a surface that was supposed to be cleansed.

Do not confuse inhibition layer with true undercure. Undercure is a chemical-failure problem: wrong lamp, wrong time, too-thick application, dirty bulbs, or mixing systems. Inhibition layer is a thin oxygen-affected skin on an otherwise specified cure. If the gel squishes, moves, or leaves a thick wet film on the wipe, that is not just inhibition. That product is not finished polymerizing. Putting the client under a dryer as if it were polish will not rescue it.

Contamination ruins polymerization

Polymerization is picky. Contamination changes the reaction.

Water in monomer is a classic ruin. Moisture in the liquid, a wet brush dunked straight from a rinse cup into the dappen, or condensation in a bottle left open beside a steam pedicure station can haze, crystallize, or slow or stop a clean acrylic set. Keep monomer closed. Do not store it next to a bubbling foot spa as if it were conditioner. Water is not an initiator. It is a contaminant in EMA liquid.

Dirty dappen dishes add leftover polymerized crumbs, dust, primer residue, disinfectant, and old pigment. Those extras steal initiator balance, seed lumps, and drag yesterday's polymer into today's bead. A dappen is a mixing vessel, not a week-long soup. Clean it. Do not disinfect a dish and then pour monomer onto still-wet disinfectant. Disinfectant in the liquid is contamination, not extra sanitation of the chemistry.

Other contamination routes: oil or emollient left on the plate; sunscreen or lotion the client just put on; mixing leftover monomer from an open dish all afternoon; dipping a brush that touched skin back into the liquid. Each one is a chemical-interaction failure, not bad luck. WAC 308-20-110(1)(g) already wants liquids in clean closed labeled containers and no careless redipping of client-contacted product. Chemistry agrees with sanitation.

Incompatibilities: systems do not all marry

Do not mix product systems as if monomer were generic water. Brand A's powder may carry a different benzoyl peroxide level than Brand B's liquid expects. Gel base from one line may not polymerize correctly under another line's lamp schedule. A wrap resin is cyanoacrylate chemistry; an acrylic liquid is EMA chemistry. Pouring them together is not a custom hybrid you discovered in Puyallup. It is an uncontrolled reaction.

Using MMA as a stronger monomer is both a chemistry incompatibility with trained EMA systems and a Washington prohibition taught in Section 10.3. MMA polymerizes into a very rigid plastic that does not behave like EMA overlays and is associated with damage and difficult removal. Mixing MMA liquid into an EMA powder because a seller promised never-break nails is still mixing an incompatible, prohibited monomer into the dish.

Layering gel over uncured acrylic, or the reverse, incorrectly is a chemical-interaction trap. If the acrylic has not polymerized, the gel's photoinitiators and the acrylic's peroxide system are not a licensed hybrid you invented at the table. Uncured layers trap wet chemistry, cause lifting, heat spikes, and sensitization. If a manufacturer publishes a specific dual system, follow that system. If they did not, do not stack wet product families because a client wanted both.

Acetone on some gels versus wraps is another incompatibility. Wraps and many acrylics and soft gels are designed to soak. Many hard gels are much more solvent-resistant; acetone will not melt them in the same minutes you use for a wrap. Using a 10-minute wrap soak on a hard gel and then prying is how plates tear. Conversely, soaking a wrap like a hard gel because acetone is acetone still needs the wrap's actual instructions — fibers and cyanoacrylate do not always leave the way a soak-off gel polish does. Physical soak-off only works as well as the polymer's solubility. Hard gel's chemical network is built to resist that solvent.

Salon scenario — Spokane polish versus gel. A client asks why gel needs a lamp if polish does not. Polish is physical evaporation. Gel is chemical photocure. Different change.

Salon scenario — Yakima wet beads. A student keeps flooding EMA so the bead looks like a water droplet. The set is slow and the sidewalls lift. Correct the mix ratio. Do not add lamp time; acrylic is not gel.

Salon scenario — Everett dirty dappen. Monday's monomer dish still holds Friday crumbs. Tuesday's beads lump and crystallize. Clean closed containers, not a community soup.

Salon scenario — Vancouver, WA hard gel pry. A tech soaks a hard gel for the same minutes used on a wrap, then pries. Acetone did not make that system a wrap. Stop, use the removal method the system requires, and do not treat all polymers as one soak.

Salon scenario — Kent stack. A booth renter layers builder gel over still-gummy acrylic to save the set. That is incompatible, uncured stacking. Remove and restart with one lawful, fully polymerized system.

Keep the exam sentence short: physical change does not make a new substance; polymerization does. Ratio, oxygen, contamination, and mixed systems decide whether that reaction is the one you wanted.