Heat the area you want to adjust using a hairdryer on low heat for 20–30 seconds, or soak just that section in warm (not boiling) water for 30–60 seconds. Once the acrylic feels slightly pliable, apply gentle pressure with your thumbs to bend the frame, temple arms, nose bridge, or ear tips, then hold in position until it cools and sets. Never bend acrylic cold. Small, repeated adjustments always outperform one big force.
I have adjusted thousands of pairs of glasses over 11 years. I have seen frames snapped in half because someone read a blog that said “just bend it.” I have seen people pay to replace lenses that cracked because the adjustment was done while the plastic was still cold. This guide will not do that to you. Everything here is what I actually do at the dispensing table, not what looks good in a list.
Why Acrylic Frames Behave Differently From Metal
This is the thing most guides skip, and it is the reason most DIY adjustments fail.
Metal frames, titanium, stainless steel, can often be bent with light manual pressure or padded pliers, because the material has flex built into it. Acrylic (also sold as acetate, cellulose acetate, or plastic frame) is rigid at room temperature. If you apply force to a cold acrylic frame, one of two things happens: either nothing moves at all, or the frame snaps. There is very little in between.
Heat changes everything. Once acrylic reaches roughly 60–70°C, it softens enough to bend under finger pressure alone. This is not a trick, it is how professional opticians do it too. The professional tool used in optical shops is called a frame heater, a small electric device that blows controlled warm air around the frame. At home, a hairdryer or warm water achieves the same result if used correctly.
Critical — Before You Start
There is one type of “plastic” frame that will not respond to this: TR-90, memory plastic, and nylon-based frames. These are designed to snap back to their original shape. If you heat them and bend them, they will spring back once cool — or worse, they will crack. Check the inside of your frame arm for the material label. If it says TR-90, stop and see an optician.
What You Actually Need (No Fancy Tools)
You do not need an optician’s tool kit. You need:
- A hairdryer — any brand, as long as it has a low or medium heat setting
- A bowl of hot tap water (not kettle water — tap hot is the right temperature)
- A small flathead or cross-head screwdriver — an eyeglass repair kit from the pharmacy works fine
- A microfibre cloth or clean towel to protect lenses
- A mirror you can stand in front of while wearing the glasses
That is the honest list. You will see some guides recommend padded pliers and precision tools. Those are helpful if you plan to do this regularly. For a one-off home adjustment, they are not necessary.
Step-by-Step: Adjusting the Temple Arms (The Most Common Fix)
Temple arms, the parts that run along the side of your head and hook behind your ears, are responsible for most fit complaints. Glasses that slide down your nose, press into your head, or leave marks behind your ears all trace back to this area.
If the glasses slide down your nose
The temple tips (the curved ends that hook over your ears) are not curving down firmly enough. Here is how to fix that:
- Hold your hairdryer about 10–15 cm from the temple tip. Run it on medium heat for 20–25 seconds. Move it slowly — you want even heat, not a hot spot.
- Touch the tip with the back of your hand. It should feel warm, not hot. If it is hot to the touch, you have overheated it — wait 30 seconds before handling.
- Using both thumbs, gently press the tip downward. You are increasing the curve that sits behind your ear. Hold for 30 seconds while it cools.
- Put the glasses on and check the fit. The tip should sit snugly behind your ear without digging in. Repeat in small increments if needed.
If the arms press too tight against your head
- Heat the section of the arm right at the hinge — where the arm connects to the front frame — for 20 seconds.
- Hold the front frame steady with one hand. Use the other to gently push the heated arm outward, away from your head, by just a few millimetres.
- Hold in position while it cools. Do both sides equally — asymmetric adjustments are the most common cause of glasses sitting crooked.
From the Dispensing Table
When I adjust temple arms, I always do the following test before I call it finished: I place the glasses flat on a table. Both temple arms should lie flat simultaneously, with no rocking. If one arm lifts off the surface, the frame will sit crooked on your face no matter how well the individual adjustments feel.
Adjusting the Nose Bridge
Most acrylic frames have a fixed, moulded nose bridge, unlike metal frames, which have small adjustable pads. This means nose bridge work is about changing the angle and width of the bridge section of the front frame itself.
If the glasses sit too low on your nose
You need to narrow the bridge slightly so it grips higher. Heat the bridge area for 25–30 seconds and very gently press both sides of the bridge inward with your thumbs. A movement of 1 mm can raise the fit noticeably. This is one of the trickiest DIY adjustments because the bridge is close to the lenses. Keep heat away from the lenses themselves.
If the bridge pinches and leaves marks
The opposite problem: you need to widen the bridge. Apply heat to the bridge and use your thumbs to press outward gently. If your frame has moulded nose pads built into the bridge, you can also stick self-adhesive silicone nose cushions over them — available at most pharmacies and online — which add padding without any bending required. This is often the easier solution.
Do Not Do This
Do not apply heat directly over your lenses, even briefly. Most prescription lenses have anti-reflective or UV coatings that will blister or haze when exposed to heat. Once that happens, the coating cannot be undone. Always target heat on the frame only, and wrap lenses in a folded microfibre cloth before you start.
Fixing Crooked Glasses (One Side Sits Higher Than the Other)
This is probably the complaint I hear most often. Crooked glasses are almost always a temple arm problem — one arm is at a slightly different angle than the other.
- Take the glasses off and place them face-down on a flat surface. Look at both temple arms from behind.
- If one arm lifts off the surface, that is the arm that is out of position.
- Heat the hinge area of the raised arm for 20 seconds. Then press it gently downward until both arms lie flat on the surface.
- Let it cool completely, then put the glasses on and check in the mirror.
One thing that surprises most people: your face is asymmetrical. Most people have one ear that sits slightly higher than the other. A pair of glasses that lies perfectly flat on a table may still look slightly tilted when worn. Always make your final judgement while wearing the glasses in front of a mirror — not while looking at them on a table.
Tightening Loose Screws
If your glasses feel wobbly at the hinge, or if a temple arm moves up and down with a clicking feeling, you almost certainly have a loose or worn screw. This is the easiest fix of all.
- Lay the glasses flat on a cloth. Find the small screws at the hinges — one on each side.
- Use the correct screwdriver head (usually a tiny flathead) and turn clockwise to tighten. Stop the moment you feel resistance — overtightening can strip the thread or crack the frame around the screw hole.
- Open and close the arm. It should move smoothly with a light tension. If it sticks or feels stiff, you have gone too far — back off slightly.
- If the screw keeps coming loose within days, add one small drop of clear nail polish to the screw threads before reinserting. This locks it without permanent adhesive and can be undone if you ever need to.
Quick Reference: Common Problems and Their Fixes
| The Problem | Root Cause | The Fix |
|---|---|---|
| Glasses slide down the nose | Temple tips not curved enough behind ears | Heat tips, increase downward curve |
| Tight pressure on sides of head | Temple arms angled too inward | Heat hinge area, angle arms outward slightly |
| One side sits higher than the other | One temple arm at wrong angle | Heat and press raised arm down; test flat on table |
| Bridge pinches, leaves red marks | Bridge too narrow or nose pads too hard | Widen bridge with heat, or add silicone nose pads |
| Glasses feel wobbly at the hinge | Loose screw | Tighten screw; use nail polish to hold if recurring |
| Glasses too wide, keep falling off | Frame width too broad for face | Heat bridge, press sides inward; or see optician |
| Tips dig painfully behind ears | Tips curved too sharply | Heat tips, reduce the curve slightly |
What I Have Seen Go Wrong (And How to Avoid It)
Over 11 years, the same mistakes come through the door repeatedly. Here are the ones worth knowing:
- Using boiling water. Hot tap water softens acetate safely. Boiling water can blister the surface finish, warp the frame unevenly, and — if you are not careful — damage your hands. The difference in pliability between 60°C and 100°C is not worth the risk.
- Bending in the wrong place. The most vulnerable part of an acrylic frame is the area immediately around the lens cutout. Stress cracks start there first. Never apply pressure near the lens rim. Work on the arms and bridge only.
- Making one big adjustment instead of three small ones. Acrylic has memory. A small bend held while cooling sets the shape cleanly. A large force bend often results in the frame partially springing back, or cracking at the stress point. Three small adjustments, each held for 30 seconds, give a more reliable result than one aggressive bend.
- Adjusting both sides without checking between each. Do one side. Wear the glasses. Check in the mirror. Then do the other. Adjusting both sides without testing in between is how you end up with glasses that are wrong in a new and interesting way.
Frequently Asked Questions
Can I adjust acrylic glasses without a hairdryer?
Yes. Warm tap water works just as well. Fill a bowl with hot tap water and submerge only the section you want to adjust for 30–60 seconds. Remove it, dry it quickly, and make your adjustment while it is still warm. The result is the same as using a hairdryer. Some opticians actually prefer water because the heat is more even and controlled.
How do I know if my plastic frames are acetate or TR-90?
Check the inside of the temple arm for a printed or stamped material code. Acetate frames feel heavier and slightly denser. TR-90 frames are extremely lightweight and often have a matte texture. If you bend a TR-90 frame slightly and it springs back to its original shape immediately, that is your confirmation — it is memory plastic and should not be heat-adjusted at home.
My frames have been adjusted several times. Is there a point when I should stop?
Yes. Each heating and bending cycle slightly fatigues the material. After four or five significant adjustments to the same spot, the acrylic starts to lose its structural integrity. If you notice the frame feels more brittle, or if stress whitening appears around hinge areas, stop adjusting and see an optician. Some frames simply reach the end of their adjustable life.
Will an optician charge me to adjust my glasses if I didn’t buy them there?
Most independent opticians will adjust glasses for free or for a very small fee regardless of where they were purchased. It takes under ten minutes and builds goodwill. Large optical chains may be stricter about this. If you are unsure, call ahead and ask. The adjustment itself takes less time than the conversation about whether they will do it.
Can I adjust glasses that have anti-reflective coating on the lenses?
Yes, but keep heat away from the lenses entirely. The coating on AR lenses is heat-sensitive. Wrap the lenses in a folded microfibre cloth before applying any heat, and make sure your hairdryer or water contact is restricted to the frame only. The adjustment itself does not affect the lenses — only heat exposure does.
Final Word
The One Rule That Covers Everything
If there is one thing to take from this guide, it is this: acrylic frames are fully adjustable, but only when warm. Heat before you bend, go slowly, and test after every small change. You have more control than most guides suggest — and less margin for error than most guides admit.
If after three attempts the fit still is not right, or if the frame is showing any signs of stress — white marks around hinge areas, hairline cracks near the lens edge, or a hinge that moves with a grinding sensation — take it to an optician. A professional adjustment costs next to nothing, and a replacement frame costs significantly more.
Everything else in this guide is what happens in between.