DaHen
New member
- Sep 6, 2010
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Headlight Restoration-new UV sealant idea
- Thread starter HotRod
- Start date
Yours is a common problem with the spar method. My guess is that there are 3 factors contributing to your situation:
1. Thin coating. The thicker the coating, the more UV it can handle.
2. Poor adhesion. Coating not sticking. May be because surface was contaminated or too smooth. I always recommend sanding only to 1500 or 2000 grit, no polish or compound, then scrub twice before applying spar. Also, keep spar to solvent ratio as high as conditions will allow. Theoretically, you'd get the best coating at 100% spar, but this is difficult to apply.
3. Environment. These headlights get hammered at the top with UV. This is where it will fail first.
ray6
1. Thin coating. The thicker the coating, the more UV it can handle.
2. Poor adhesion. Coating not sticking. May be because surface was contaminated or too smooth. I always recommend sanding only to 1500 or 2000 grit, no polish or compound, then scrub twice before applying spar. Also, keep spar to solvent ratio as high as conditions will allow. Theoretically, you'd get the best coating at 100% spar, but this is difficult to apply.
3. Environment. These headlights get hammered at the top with UV. This is where it will fail first.
ray6
In all the headlights i've restored, i always used only 1 coat of spar/ms. My restored ones have passed over 5 months test pretty good, and they are still holding up. And for me it seems that even if you try to touch up a missed spot before 10 seconds, it streaks. So yeah, the best way is to wipe light down with ms and start over.
A TIP i want to share with you guys. Never found on this thread anyone giving advice on this one: To mix the spar/ms I do a 60/40 mix, using a 3.5" diameter x 2.5" height plastic disposable cup (originally used as a jelly mold, i think). I use a syringe to measure 20 milimeters of water, pour it into the mold, and use a permanent marker to mark the 20ml. Then, measure 24ml of water, pour it in the same mold, and mark the other 24mls. Dispose water (recycle it), and dry the mold. Then, with a disposable spoon i take OMS and pour it into the first 20mls. In the other 24mls, i pour the spar with another spoon. I then mix them using 2 toothpicks pretty well. Apply the mix on headlights using the folded blue towels trick. Blue towels is the best thing to apply it IMO. BTW i make many (about 10) marked molds, so when i am working (i am mobile), i just take one marked mold, and mix spar/ms
And something that has been told before but i want to emphazise is to prepare the freshly sanded or buffed headlights thoroughly, using rubbing alcohol or mineral spirits. MS works better IMO. It happened me that on the first set of lights i did, i didn't prep the left one, and 2 months later while i was washing the car, i was cleaning the light, and after drying i found a 1" x 3" slot on the middle of the light showing the sanded surface, and another one smaller on a corner.
Another possibility is to mix in a 1/2 to 1 oz. plastic cup like the ones used in restaurants for ketchup, etc. Available at restaurant supply companies. Also, to get a better consistancy, try using foam applicators like the ones sold in drug stores for applying makeup.
CAUTION: cups need to be made from PET or HDPE. Some are styrofoam or other plastics. Always test first by mixing coating in cup and wait to see if the coating dissolves the cup. Never use paper cups. Some are coated with wax (will contaminate coating) or plain paper which will soak through.
Foam applicators may be made with latex which can contaminate solvent based coatings. Test first. When you find a brand that works, don't change brands. Some products are marked as latex free, some are not.
ray6
Re: Headlight Restoration-neyw UV sealant idea
The best pix would be outdoors in the shade. If possible, using a polarizer filter will also help.
I camera is adjustable, use a tripod and longer shutter speed to stop down lens. This will give you sharper focus and greater depth of field.
Never use flash.
Move the camera around while looking at screen or through viewfinder to minimize reflections and get the best angle.
For the best before and after pix, mount the camera on a tripod and take a pix, restore the headlight, then take another without moving the camera.
Headlights on tend to show every wart. Difficult to restore headlights that will look crystal clear with lights on.
ray6
The best pix would be outdoors in the shade. If possible, using a polarizer filter will also help.
I camera is adjustable, use a tripod and longer shutter speed to stop down lens. This will give you sharper focus and greater depth of field.
Never use flash.
Move the camera around while looking at screen or through viewfinder to minimize reflections and get the best angle.
For the best before and after pix, mount the camera on a tripod and take a pix, restore the headlight, then take another without moving the camera.
Headlights on tend to show every wart. Difficult to restore headlights that will look crystal clear with lights on.
ray6
How to prevent runs
Did my first on a personal car -- a 2002 sequoia that has not been paid much attention.
Followed the plan well -- chemicals, wet sanding 800/100/1500, then application of spar of 50%/50%.
All looked great with the exception of runny spar on the headlights. Lots of runs, almost at each horizonal pass.
Do you think this was too much product on the scott towel, or do you think my mix of spar/mineral spirtis was too thick or thin?
I satuarted the scott towel -- perhaps I should have pressed out some of the spar before wiping?
Do you guys find that a really thin coat is best to prevent runs?
Will the mix affect this, e.g., would more poly say to 60% or 70% be thicker and prevent the runs?
What are your experiences?
Thanks.
David
Did my first on a personal car -- a 2002 sequoia that has not been paid much attention.
Followed the plan well -- chemicals, wet sanding 800/100/1500, then application of spar of 50%/50%.
All looked great with the exception of runny spar on the headlights. Lots of runs, almost at each horizonal pass.
Do you think this was too much product on the scott towel, or do you think my mix of spar/mineral spirtis was too thick or thin?
I satuarted the scott towel -- perhaps I should have pressed out some of the spar before wiping?
Do you guys find that a really thin coat is best to prevent runs?
Will the mix affect this, e.g., would more poly say to 60% or 70% be thicker and prevent the runs?
What are your experiences?
Thanks.
David
Re: How to prevent runs
David-
Runs usually mean your coating is too thin, or you are applying too thick a coating. Never been a big fan of the paper towel technique. Too subjective. How much coating to apply? How much pressure to apply, etc.
I would try the foam applicator application method we use. Would probably work just as well with the spar/mineral spirits. Tends to automatically apply the right thickness.
I would also try mixing your spar/MS thicker, say 80 spar/20 ms. This would give you a thicker coating with less chance of runs, but may cure too quickly if it is hot ar low humidity.
If you go with the foam, try cross coating as we show in our videos.
One problem with the foam/cup technique, you have to be aware of the materials used. The foam applicators should be latex free for solvent based coatings. Cups must not be wax coated paper.
Hope this helps.
ray6
David-
Runs usually mean your coating is too thin, or you are applying too thick a coating. Never been a big fan of the paper towel technique. Too subjective. How much coating to apply? How much pressure to apply, etc.
I would try the foam applicator application method we use. Would probably work just as well with the spar/mineral spirits. Tends to automatically apply the right thickness.
I would also try mixing your spar/MS thicker, say 80 spar/20 ms. This would give you a thicker coating with less chance of runs, but may cure too quickly if it is hot ar low humidity.
If you go with the foam, try cross coating as we show in our videos.
One problem with the foam/cup technique, you have to be aware of the materials used. The foam applicators should be latex free for solvent based coatings. Cups must not be wax coated paper.
Hope this helps.
ray6
Part-timer
New member
- May 30, 2011
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Re: How to prevent runs
David,
If you saturated the scott towel, thats your mistake. I take a scott blue towel....fold it in half....then cut a strip 2 1/2" wide. Fold that in half and then just dip it in the spar mixture (I use 70/30 unless its quite windy) for a second. Itry to get an even line across the towel about 1" from the top of the towel you are going to swipe from. If you saturate the entire towel....way too much!!! (unless you are doing a huge headlight lens, like a newer chevy/ford truck) Most headlights....1" is plenty. In my opinion...the trick is to apply the coating over the entire lens within 15-20 seconds. If ya keep playin with it, you'll have streaks! I circle the whole lens first to make certain I get all edges completely. Then fill the middle with(same towel) and then swipe across horizontally to finish. Thats it! Gravity should do the rest for you.
David,
If you saturated the scott towel, thats your mistake. I take a scott blue towel....fold it in half....then cut a strip 2 1/2" wide. Fold that in half and then just dip it in the spar mixture (I use 70/30 unless its quite windy) for a second. Itry to get an even line across the towel about 1" from the top of the towel you are going to swipe from. If you saturate the entire towel....way too much!!! (unless you are doing a huge headlight lens, like a newer chevy/ford truck) Most headlights....1" is plenty. In my opinion...the trick is to apply the coating over the entire lens within 15-20 seconds. If ya keep playin with it, you'll have streaks! I circle the whole lens first to make certain I get all edges completely. Then fill the middle with(same towel) and then swipe across horizontally to finish. Thats it! Gravity should do the rest for you.
davidc11291
New member
- Oct 14, 2011
- 200
- 0
Re: How to prevent runs
Spar application has been giving me fits lately. I first tried it back in the Spring. It worked great when the temps were in the low 80's, but now that we're right around 100 degrees, it's drying too fast on me. You're definitely right about having to apply it to the whole lens within 15-20 seconds. 3 questions for you-
1) Are you able to successfully apply it outdoors in 100 degree heat with a 70/30 mix using your application method?
2) I find myself going back to the bucket to redip my blue towel in spar during application. I usually redip twice during each headlight application. After reading your post, it seems pretty obvious that redipping is the source of my problems. Are you able to apply without ever redipping?
3) Please explain how you fold and saturate the towel, cause I just can't picture it. Fold in half, the cut a strip 2 1/2" wide, then fold that long ways, so you've got a strip about an inch or so wide, and 6 inches long? Then you just dip the last inch or so of that strip into the spar and apply?
Spar application has been giving me fits lately. I first tried it back in the Spring. It worked great when the temps were in the low 80's, but now that we're right around 100 degrees, it's drying too fast on me. You're definitely right about having to apply it to the whole lens within 15-20 seconds. 3 questions for you-
1) Are you able to successfully apply it outdoors in 100 degree heat with a 70/30 mix using your application method?
2) I find myself going back to the bucket to redip my blue towel in spar during application. I usually redip twice during each headlight application. After reading your post, it seems pretty obvious that redipping is the source of my problems. Are you able to apply without ever redipping?
3) Please explain how you fold and saturate the towel, cause I just can't picture it. Fold in half, the cut a strip 2 1/2" wide, then fold that long ways, so you've got a strip about an inch or so wide, and 6 inches long? Then you just dip the last inch or so of that strip into the spar and apply?
langman37
New member
- Mar 3, 2006
- 76
- 0
I don't think anyone feels that way Ray6, continue posting.
Respectfully disagree.
The man is using his PROFESSIONAL experience to add to the conversation. Appears to me, that he is only talking of 'his products' as an example.
Bill
To be honest, hidden agenda or not, I find his posting more useful than me trying to google for years, and for that I truely appreciate it. If only I have come across them earlier, I could probably speed up my learning process and avoid some costly mistakes. Then again, I guess I won't appreciate his sharing as much if not for those painful experiences. Not to flame, just my 2 cents..
As the temperature increases, or humidity decreases, you'll have to add more solvent to slow down the drying. This will give you more working time, but a thinner coat. I'd try 60/40, and after the first wipe, if not right, wipe it off and add more solvent or mix a new batch at 50/50.
This is the type of application whereby the spar/solvent method starts to become a problem. A better approach might be a water based coating such as Delta Kits. Or, carry both and choose based on weather.
Water based coatings usually require 2 coats due to their thinness, but cure time is 3 or 4 minutes between coats. More costly initially ($100) but probably less than a dollar per headlight.
Water based coats require a better finish though, and would finish to 3000 grit. As an added bonus, this coating can be applied in direct sun.
I have no association with Delta Kits. They just sell a good product.
ray6
This is the type of application whereby the spar/solvent method starts to become a problem. A better approach might be a water based coating such as Delta Kits. Or, carry both and choose based on weather.
Water based coatings usually require 2 coats due to their thinness, but cure time is 3 or 4 minutes between coats. More costly initially ($100) but probably less than a dollar per headlight.
Water based coats require a better finish though, and would finish to 3000 grit. As an added bonus, this coating can be applied in direct sun.
I have no association with Delta Kits. They just sell a good product.
ray6
Last edited:
You might also try using a foam applicator instead of folded towel. Much easier to control coating thickness.
These are the same as what women use to apply makeup. Available from most drug stores. Only problem is they should be latex free if using spar method. Fine for water based. If you find a brand that works, don't change.
These are the same as what women use to apply makeup. Available from most drug stores. Only problem is they should be latex free if using spar method. Fine for water based. If you find a brand that works, don't change.
Thanks, Bill for your support.
Chemistry 101
It might be helpful to those just getting into headlight restoration to learn a little chemistry (don't groan, this won't take long).
The reason headlights turn cloudy is because the factory applied protective coating turned cloudy. Polycarbonate has no natural protection and must be shielded from UV and moisture. The factory applied the original coating for a reason. Headlight must pass an exposure test or they can't be used on U.S. vehicles.
Sealing is easy. UV protection is not.
The way most of these coatings work is by converting light of a specific wavelength (UV) to molecular heat. This is on an atomic level. Don't look for any flames, but you can feel it as a hot surface.
UV causes certain molecules (UV adsorbers) to dance the fire dance. Most UV adsorbers are based on silicone, phenolic resin, etc. As these poor molecules dance the dance of death, they vibrate faster and faster (basic physics). At some point, they jump right out of their little nests. This causes a loss of clarity and yellowing.
Basically, they have broken ranks with their brothers and are no longer hooked together (cross-linked).
So, this brings up the first critical point. More molecules, more dance of death capability. The thicker the coat, the longer it will adsorb UV.
This is why you may see variable results using the spar/ms method. How thick is the coat? Is it even thickness?
Spar/ms is also sensitive to certain parameters other coatings may not be.
If you're going to use the spar method, try to set up the following
conditions:
The rougher the surface, the more surface area to hold on to.
Don't sand any more than you have to.
Spar hates water. Make sure the surface is totally moisture free. 100% alcohol/propanol is better than ms because it attracts water and dries faster.
Mix your spar/ms as thick as you can to meet current conditions. As the temperature rises or humidity lowers, increase MS. Try the coating. If it's not right, wipe off the headlight with MS and remix. Make sure to mix well.
Two coats are far better than 1, but cure time between coats is probably on the order of hours or days. Not practical if doing it for clients.
Paper towel application can be tricky and problematic. Try using a foam applicator like women use to apply makeup. Put/mix the spar/ms in a small condiment cup and dip the foam into the cup. Just make sure the cup contains no wax.
Keep in mind that paper towels, foam applicators, stripper pads, etc. should be placed in a ziplock bag when you finish. Push out all the air before sealing. This will prevent spontaneous combustion.
I always place the bags in the middle of my driveway (wife hates it) then throw them in the garbage the next day. You could also soak these materials in water then immediately throw away.
The other point is that these little orphan molecules that have broken from the pack are easy to remove with certain chemical solutions. This is why strippers and cleaners easily strip off these loners but have little effect on the others.
Waxes contain UV adsorbers, but the coatings are extremely thin and are easily removed by car washing, so wax based protective coatings are short lived.
Because coating thickness is such a crucial factor I am suspicious of any thin, uncured coating really protecting polycarbonate.
As far as coating lifetime, there will always be comments about how long a certain coating has lasted. The problem is this:
There are so many variables that it is impossible to predict a coating's lifetime without taking all the variables into consideration. For example:
Let's say I refinished my headlights with Log Cabin syrup and they look brand new 5 years after I restored them (except for the ants).
But if I keep my car in the garage, and at I park at work in a garage, and I live in Seattle, this story could be true.
On the other hand, I could use a professional coating sprayed on, UV cured, etc. But it only lasted 9 months because I live in Florida, I drive a PT Cruiser (almost horizontal UV exposure) park outside facing south and don't drive often. Taking it further, the driver's headlight is bad but the passenger's is fine because the sun is blocked on this headlight by a tree.
You see how difficult predicting lifetime is.
So, my suggestion is to try to get the thickest coating possible regardless of the material. If using the spar/ms method, mix to get the best performance depending on the weather. Don't finish any smoother than you need to to get better adhesion.
Even if you are happy with the spar/MS, it would be nice to have another type of coating (probably water based) for those special situations.
ray6
Chemistry 101
It might be helpful to those just getting into headlight restoration to learn a little chemistry (don't groan, this won't take long).
The reason headlights turn cloudy is because the factory applied protective coating turned cloudy. Polycarbonate has no natural protection and must be shielded from UV and moisture. The factory applied the original coating for a reason. Headlight must pass an exposure test or they can't be used on U.S. vehicles.
Sealing is easy. UV protection is not.
The way most of these coatings work is by converting light of a specific wavelength (UV) to molecular heat. This is on an atomic level. Don't look for any flames, but you can feel it as a hot surface.
UV causes certain molecules (UV adsorbers) to dance the fire dance. Most UV adsorbers are based on silicone, phenolic resin, etc. As these poor molecules dance the dance of death, they vibrate faster and faster (basic physics). At some point, they jump right out of their little nests. This causes a loss of clarity and yellowing.
Basically, they have broken ranks with their brothers and are no longer hooked together (cross-linked).
So, this brings up the first critical point. More molecules, more dance of death capability. The thicker the coat, the longer it will adsorb UV.
This is why you may see variable results using the spar/ms method. How thick is the coat? Is it even thickness?
Spar/ms is also sensitive to certain parameters other coatings may not be.
If you're going to use the spar method, try to set up the following
conditions:
The rougher the surface, the more surface area to hold on to.
Don't sand any more than you have to.
Spar hates water. Make sure the surface is totally moisture free. 100% alcohol/propanol is better than ms because it attracts water and dries faster.
Mix your spar/ms as thick as you can to meet current conditions. As the temperature rises or humidity lowers, increase MS. Try the coating. If it's not right, wipe off the headlight with MS and remix. Make sure to mix well.
Two coats are far better than 1, but cure time between coats is probably on the order of hours or days. Not practical if doing it for clients.
Paper towel application can be tricky and problematic. Try using a foam applicator like women use to apply makeup. Put/mix the spar/ms in a small condiment cup and dip the foam into the cup. Just make sure the cup contains no wax.
Keep in mind that paper towels, foam applicators, stripper pads, etc. should be placed in a ziplock bag when you finish. Push out all the air before sealing. This will prevent spontaneous combustion.
I always place the bags in the middle of my driveway (wife hates it) then throw them in the garbage the next day. You could also soak these materials in water then immediately throw away.
The other point is that these little orphan molecules that have broken from the pack are easy to remove with certain chemical solutions. This is why strippers and cleaners easily strip off these loners but have little effect on the others.
Waxes contain UV adsorbers, but the coatings are extremely thin and are easily removed by car washing, so wax based protective coatings are short lived.
Because coating thickness is such a crucial factor I am suspicious of any thin, uncured coating really protecting polycarbonate.
As far as coating lifetime, there will always be comments about how long a certain coating has lasted. The problem is this:
There are so many variables that it is impossible to predict a coating's lifetime without taking all the variables into consideration. For example:
Let's say I refinished my headlights with Log Cabin syrup and they look brand new 5 years after I restored them (except for the ants).
But if I keep my car in the garage, and at I park at work in a garage, and I live in Seattle, this story could be true.
On the other hand, I could use a professional coating sprayed on, UV cured, etc. But it only lasted 9 months because I live in Florida, I drive a PT Cruiser (almost horizontal UV exposure) park outside facing south and don't drive often. Taking it further, the driver's headlight is bad but the passenger's is fine because the sun is blocked on this headlight by a tree.
You see how difficult predicting lifetime is.
So, my suggestion is to try to get the thickest coating possible regardless of the material. If using the spar/ms method, mix to get the best performance depending on the weather. Don't finish any smoother than you need to to get better adhesion.
Even if you are happy with the spar/MS, it would be nice to have another type of coating (probably water based) for those special situations.
ray6
I hope Ray stays around. If anything, he has given us leads to companies marketing the "professional" products by mentioning them in his posts. I followed up on some of them and found that although their marketing does not target the DIYers, neither does it exclude them. Your money is just as good as that of the professional, once you find the vendors.
Part-timer
New member
- May 30, 2011
- 219
- 0
Re: How to prevent runs
This is so much easier in person....lol
Ok, a blue scott's towel measures approx.....10 1/2" X 11".
Fold the towel in half on the 11" side, giving you a towel that measures 10 1/2" X 5 1/2".
I just do this by looking....but to be precise....measure 2 1/2"..down the 10 1/2" side.
Now you have a strip that is 2 1/2" X 5 1/2".
Fold that in half so you then have 2 1/2" X about 2 1/2".
Then just dip the rounded part, that you just folded over, into the spar mixture and let it soak in the length of the fold to about an inch into the dry part of the towel. This should only take a second or two. Then start applying to the lens. (See picture) No re-dipping is needed. For larger lenses....I cut larger pieces than 2 1/2" wide, in order to swipe a wider path. Still no re-dipping needed. I have been doing this in Daytona Beach Florida for almost 3 years now, outside in the heat. I must admit that I schedule my jobs in advance to avoid working in the hottest part of the day, unless you have a canopy. I have learned to taylor my mixture ratios to the weather conditions though...but as of today am mostly using between 70/30 and 60/40. I also use a bigger sized cup, so that I'm not trying to shove a 3" towel in a 1" container of mix. I have tried using those foam applicators, but found that for me, they would run dry of mixture before coating the whole lens....unlike the scott's towels. I do use a different piece of scott towel for each lens.
This is so much easier in person....lol
Ok, a blue scott's towel measures approx.....10 1/2" X 11".
Fold the towel in half on the 11" side, giving you a towel that measures 10 1/2" X 5 1/2".
I just do this by looking....but to be precise....measure 2 1/2"..down the 10 1/2" side.
Now you have a strip that is 2 1/2" X 5 1/2".
Fold that in half so you then have 2 1/2" X about 2 1/2".
Then just dip the rounded part, that you just folded over, into the spar mixture and let it soak in the length of the fold to about an inch into the dry part of the towel. This should only take a second or two. Then start applying to the lens. (See picture) No re-dipping is needed. For larger lenses....I cut larger pieces than 2 1/2" wide, in order to swipe a wider path. Still no re-dipping needed. I have been doing this in Daytona Beach Florida for almost 3 years now, outside in the heat. I must admit that I schedule my jobs in advance to avoid working in the hottest part of the day, unless you have a canopy. I have learned to taylor my mixture ratios to the weather conditions though...but as of today am mostly using between 70/30 and 60/40. I also use a bigger sized cup, so that I'm not trying to shove a 3" towel in a 1" container of mix. I have tried using those foam applicators, but found that for me, they would run dry of mixture before coating the whole lens....unlike the scott's towels. I do use a different piece of scott towel for each lens.