Auto Headlight Lens Dehazing

This project is certainly going to fall under the category of “& Things” in my blog and covers the method I used to refurbish our oldest car's front plastic headlight assembly lenses. Before working on them they looked more like frosted glass than a clear lens.  First some background, the car the work will be done to is a 2007 Toyota Camry that we got in the fall of 2006 which at the time of writing this is coming up on 18 years old and has about 112,000 miles on it. 

Since replacing the lens is costly, I looked at various different kits for the work and most of them that looked to be effective used the same basic process of sanding the lens and then applying a coat of UV blocker over the refurbished lens.  Some of the kits had only two grits a coarse and fine while others had 3-5 grits.  One kit had just 320 grit and 2,000 grit.  Now I have done enough sanding on wood for preparation to applying a finish like lacquer or polyurethane and on the buffing of the final coat that making a jump in grits like that is a bad idea.  To me it seems like an awful lot of time would be spent removing the initial scratches from the 320 grit paper with the 2,000 grit.  You are either going to spend forever with the fine grit or give up before the lens looks really clear and not scratched.  To do the work efficiently and end up with good results I think it’s going to take a lot more intermediate sanding grits to get a clear lens. 

Now I just happen to have a wide variety of wet/dry sandpaper and sanding pads ranging from 100 grit to 12,000 so my plan is to use them to see what kind of results are obtained.  If the results give me a nice clear lens then I will get some UV blocker to finish them off.

Here is what the lens looked like before I started with the edges masked off.  The masking is done so when I am sanding and invariably sand a little beyond the lens the body paint will not get scratched. 

The first and coarsest grit is used to get rid of all the degraded plastic on the lens, clean the surface and establish a base scratch pattern.  All of the sanding is done using water as a lubricant and to keep the paper from loading up with plastic.  Given the lens condition I decided to start the wet sanding with a silicon-carbide 320 grit sandpaper.  If the lenses had been in a little worse condition, I would have started with 220 grit.  This is what the lens looks like when done.  It ended up taking about 15 minutes which was the longest of any of the papers.  Note that the scratch pattern from sanding runs left to right.  This will come into play when I sand with the next grit.

Using a finer 400 grit paper I sanded up and down until all the horizontal scratches from the 320 sanding were gone.  The bottom left photo shows the 320 grit scratch pattern and the right photo has been vertically sanded with 400.  The vertical scratch pattern does not show in the photo as well as it did in real life but you get the idea. 

The process gets repeated with 600, 800, 1200, 1500 and 1800 which is the finest of my silicon sheet sand paper.  Going through all these grits didn’t take too long, probably less than two minutes each which includes drying the lens and checking the scratch patterns plus touching up any missed spots to make sure all the previous grit’s pattern had been removed.  At this point the lens while cloudy is a lot clearer than after the initial 320 grit.

Switching from sheets to foam backed pad grits starts with 2400 grit.  I use these pads when sanding film finishes like lacquer or polyurethane between coats.  The same process of wet sanding is used for 3200, 3600 and 4000 with the 4000 grit shown below.   This is right at the end of where the lens looks cloudy.  As I move on to finer grits the lens becomes increasingly clear.

After 4000 grit comes 6000, 8000 and the last sanding pad of 12000 shown below with each step making the lens noticeably clearer.

The last step before spraying on the UV blocker is to use a very fine plastic polish.  A small amount is put on the lens then a soft cotton cloth is used to rub out the remaining fine scratches which really improves the lens’s clarity.  At this point I removed the masking around the lens because it got beat up during the sanding process and I was waiting for the UB blocker to arrive.

Once the UV blocker arrived the headlight lens gets masked off.  A much larger area gets masked this time because I did not want to have any overspray of the UV blocker onto the car’s paint.

The UV blocker I used requires two coats which besides adding UV protection also made a noticeable improvement in the clarity of the lens.  The top photo shows the completed process while the bottom photo is the “before” photo.  Total time spent sanding and polishing each of the lenses was about 40-50 minutes.  For spraying the UV blocker it took longer to mask of the headlight than to spray.

While the lenses look 99% brand new the question is how long will they stay that way?  Only time will tell and my plan is to add a comment in about 6 months with an update on how they look.

Game Piece Holder – #10 Fixing a Problem in Tuning the Base & Final Finishing

When I was doing the final turning on the bottom of the bowls after the sacrificial base had been removed from the maple and cherry bowls using the jumbo set of jaws the process went pretty well except for a couple times.  In one case the bowl came party loose and the other time it popped completely out of the large jaws.  Fortunately for me the bowl that came out of the chuck still had the base on and it landed on a big pile of wood shavings which cushioned the impact.  Only damage was a couple of scratches that could be sanded out but I did have to swap the jaws to remount the piece so I could sand it.  When the bowl flew off, I knew I needed a little something to help hold the bowl in the jaws.  My solution for this was to make an attachment that puts a little pressure on the base.  It consisted of a wood turning that screws onto my live center and has the last inch or so of a pencil along with its eraser inserted into a hole in its end.  The left photo shows the piece and pencil stub that gets inserted into it while the right photo shows the completed assembly.  

In use the bowl gets mounted in the jumbo jaws and the above assembly gets screwed onto the live center.  The tail stock is then set to apply a little pressure to the base which helps keep the bowl from coming loose and go flying across the room which is a lot less stressful for me.  The pencil eraser acts as a flexible non-marring cushion against the base of the bowl.

Once the turning of the base is completed and sanded the walnut and oak bowls are ready to be sprayed with lacquer.

Before starting the finishing of these bowls, the lathe turnings from the last six bowls get swept together and it’s a pretty good pile pretty much the same size pile as the first group of six.  Out of curiosity when I had the turning blocks assembled and before any work was done on them, I had put the large bowl’s walnut and oak turning blanks on the digital kitchen scale to see how much they weighed.  My plan was to weigh them again when completed to see how much material got made into shavings.  Both of the blocks were within a couple of ounces of each other at about 2½ pounds each with the oak being a couple ounces heavier.  When finished the large walnut bowl weighed 4½ ounces and oak one weighed 5¾ ounces.  That means that for each large bowl a little over two pounds out of each blank or roughly 85% of the blank was converted into shavings hence the pile you see in the photo.

The maple and cherry bowls here have three coats of lacquer while the oak and walnut ones only have one coat so far.  A few more days of spraying the rest of the coats on and they will be done.

My process is to spray the inside of half of the bowls and on the other half spray the outside in the morning.  They are then left to cure until the afternoon when they are reversed and sprayed so each day both the outside and inside get a coat of finish.  They are then left to sit overnight and wet sanded the next morning with a 1,500 grit pad, left to dry for an hour then the process is repeated.  One difference with the last coat is to let is set for a week so to allow the lacquer to really harden before lightly wet sanding using a 3,600 grit pad to just remove any dust particles.  When done, here is what all four sets of bowls look like.

For storage the bowls are designed to nest within each other like this.

This has been an interesting project with all the different design options being explored and tested to see how they looked.  In addition, the proportions had to match across all twelve bowls as well as having all the same size bowls match between the different sets.  To make this happen I needed to come up with a repeatable process for the turning sequence which I don’t usually have to do.  While I enjoyed the challenges and am happy with the results, I am pretty sure one set of these is all there is going to be. 😊