chemical removal of yellowing white gel ?

[pescaloco]

Hey guys,

I was wondering if anyone has has sucess with solvents or acids to bring out yellowing caused by entraped styrene that has reacted with uv light in white gelcoat.

There is a company in Australia that someone mentioned to me (Top Gear)
they claim to have a chemical and buffing restoration "system"

They will sell only a complete system with a first step chemical / then compounds and buffing equipment. (very expensive)

Any clue what solvent would be efective to raise the styrene to the surface where it could be wet sanded out without excessive removal of the gelcoat.

Thanks so much,

[Fanie]

Try Amway's silicone glaze

[ondarvr]

Styrene can be from 30 to 50% of the gel coat and is chemically part of it, so I'm not sure how they would "raise styrene to the surface". There are products (chemicals) that can break down gel coat (cured base resin), but I can't see how this would work. Frequently there is a resin and styrene rich layer next to the mold surface that can yellow sooner than normal, this is typical with thick gel coat. When this surface layer turns yellow it can normally be sanded off and the yellowing may be slow(er) to return.

[Fanie]

On my gell coat I have found that only the surface layer looks dead. If you polish it with a high quality polish then the surface comes off and you get some gloss back. If the gell coat is stained you may not get it out, the stain will remain.

[mark775]

Acid. Oxalic is good. Be smart about application. Then take care of the surface.

[ondarvr]

Oxalic acid works very well on stains, but not yellowed styrene. If something was to work, it would need to penetrate into the gel coat and bleach it.

[mark775]

How does one know that it is Styrene that is yellowing?
I'd like to see a picture.

[pescaloco]

Thanks guys,

Just a little more info, there seems to be maybee several different patterens to the yellowing, some areas are striated and others are motteled looking almost like how fabric print through looks except yellow or brownish spots.

It seems in the areas that are porous and have the striated looking yellow, the yellow actually will raise to the surface after keeping the surface wet with a rag soaked with blackstreak remover on it. The yellow color becomes more intense and actually does come somewhat to the surface. Then it can be scrubed out fairly well with a cleanser and a hand pad, finally sanded and buffed back to like new.

I detail boats and do gelcoat repairs so this is something I need to deal with and really alot on a particular brand of boats.

Since I need to get results with out sanding all the mil thickness off the boat I would really like to find a solution. I am open
to all suggestions

EDIT: Just a little more info, I usually can start wet sanding with 800 or 1200 grit wetdry and remove surface yellowing, yesterday in an attempt to see just how bad the side of the superstructure was I went all the way down to 400 paper and if I kept sanding to the point where I knew things were going to go wrong very soon then the gel would turn white again.
So you can put in perspective this is a expensive 2 1/2 or 3 year old in the water boat that was not well maintained, but the condition of the gelcoat seems almost hopeless to correct.

[pescaloco]

Hey Fanie,

Can you tell me a little more about the silicone glaze.

Are you suggesting it as a way to mask the yellowing (put a shine on it) or a way to remove or lighten it ??

In spite of the yellow the gelcoat can be polished to high gloss it just looks ugly and the coloration of different parts of the boat are very uneven

Thanks

[mark775]

It is not mineral stains as I thought. I have no idea - good luck.

[pescaloco]

Hey guys here is a picture I had on file of a different boat same condtion with the gelcoat

Thanks Mark 775

[Fanie]

That does not look like yellowing to me. That looks like the gell coat wasn't applied correctly inside the mold prior to glassing or if it was the gell coat wasn't allowed to cure enough before the glassing was done. The fiberglass/resin is pressing through.

I may be mistaken though. If that is just dirt you should be able to scrub it clean. Silicon glaze is used to put on windows so water doesn't cling to it. It washes off after a while.

Or that corner of the boat was washed so much the gell coat is washed off :D

You can also try something with amonia in it, it works well to remove ie algea when you clean the boat as well.

You could match an epoxy paint with the colour and spray paint that part over if it is the gell coat that is showing the inner glass. I don't know of another method to finish it.

Maybe Par or some of the other guys can offer another opinion on it.

[pescaloco]

Thanks Fanie,

did you click on the photo to enlage it ?

The top of the shot shows a somewhat striated patteren of yellow spots, and it will come out or lighten with some pretty extreme wetsanding and polishing. Other places it almost looks like when you add a tinting agent to paint or gelcoat and it was not mixed well (how it would look in a mix cup)

I think you are probable right about the production process, because all this brand of boats seems to have the same issues in the same areas.

But the ones that are well taken care (waxed every 3 months) of do not get like this, it seems to take about 6 months from new but is subtle and really (NOT) noticible.

[Fanie]

I zoomed it, rotated it, fade in, fade out, with and without glasses, with the microscope, one eye, the quick look, the stare... :D but it is different on a picture than looking at the real thing.

Have you tried cleaning it with something ? Even laquer thinners will work to remove tough dirt. Soap and water does not always clean properly if the gell coat surface is course or pitted.

[ondarvr]

Hey guys here is a picture I had on file of a different boat same condtion with the gelcoat

Thanks Mark 775


That's from the gel coat being sprayed at a sharp angle and too thick. The pigment, fillers and resin will separate and the resin rich areas turn yellow.

Sometimes you can easily see it as soon as it comes out of the mold because the resin base is typically an amber color. Other times it can take a little while and the more sun it see's the sooner it will change color.

Its possible that its too thin, but it doesn't look like typical alligation.

Looking at it in person should make the cause easy to identify.

[mark775]

Wow! I have never seen this. How sloppy! Learned somethin' today - thx.

[pescaloco]

I almost wasn't going to say anything but I can't help it !

Since I detail boats and do gelcoat work for a living you could give a guy a little more credit (IT'S NOT DIRT) and I have tried a lot of different solvents and oxclic acid in combination with wetsanding to lighten/brighten.

I zoomed it, rotated it, fade in, fade out, with and without glasses, with the microscope, one eye, the quick look, the stare... :D but it is different on a picture than looking at the real thing.

Have you tried cleaning it with something ? Even laquer thinners will work to remove tough dirt. Soap and water does not always clean properly if the gell coat surface is course or pitted.

[Fanie]

Sorry Pescaloco,

I didn't know you do gelcoat work for a living.

I have seen similar where the surface was uneven where the guy wiped it off on the surface leaving the 'stains', when brushed it came clean.

Acids or chemicals is not going to fix your problem. Sand and spray with a good quality epoxy paint is my best call, but then, you probably already know it by now.

[pescaloco]

That's from the gel coat being sprayed at a sharp angle and too thick. The pigment, fillers and resin will separate and the resin rich areas turn yellow.

Sometimes you can easily see it as soon as it comes out of the mold because the resin base is typically an amber color. Other times it can take a little while and the more sun it see's the sooner it will change color.

Its possible that its too thin, but it doesn't look like typical alligation.

Looking at it in person should make the cause easy to identify.


Ondarvr

That particular picture the the surface was rough and had open pores, I have found that areas that do have a rough crazed looking surface I can soak rags with something (I have tried acetone / mek / bleach / thinner) but what every the chemicals are in Black streak remover they actually seam to float some of the yellow/amber or raise it so it can then be scrubbed off with out excessive sanding and gelcoat remvoval.

Back to that company in Australia, can you think of a chemical or combination of chemicals that could remove or bleach the amber color back to white. This is a huge problem for me, but I'm not going to spend $500.00 or $800.00 for the Top Gear yellow removal KIT that does a 25 foot boat.

thanks to all for you interest and suggestions

[ondarvr]

The solvent used may be removing some of the resin, which will lighten the color and also deepen the low spots. The problem is in the original gel coat process though, so to fix it, it will need to be resprayed.

[pescaloco]

The solvent used may be removing some of the resin, which will lighten the color and also deepen the low spots. The problem is in the original gel coat process though, so to fix it, it will need to be resprayed.

Thanks I have been away for a few days.

Would one consider clear gelcoat or a weakly pigmented mix of duratec/white gelcoat a good way to fill surface porosity and replace mil thickness that was lost to sanding.

Example base coat/clear coat like in automotive paint systems.

I would like to fill the surface porosity and restore the gelcoat thinkness, WOULD clear gelcoat and duratech high gloss or what ever combination of pigmented and clear gelcoat in combination with the Duratech high gloss give a non porous surface finish and have some UV protection from the use of the Duratec.

What do you think ?

Thanks

[Wynand N]

Ondarvr is right - separation took place between resin /styrene.
My take on it is that the gelcoat was thinned more than the usual max 5% styrene to volume to make spraying easy and overdone the thickness in the effected areas. The laminate probably still went on whilst gelcoat still tacky, trapping excess styrene in gelcoat that did not evaporated...

To fix? I would take and orbital sander and sand affected areas clean. Then mix gelcoat (can easily be colour matched), add some wax and spray again. Work down with water sandpaper until smooth, apply P11 with buff and polish.

[Itchy&Scratchy]

You might find that the manufacturer uses silicone based release waxes or permanent release with silicone base,this causes pre- release, whch is what this might be.
Tried a silicone release wax many years ago-------NEVER AGAIN-absolute sh..t!!!
J

[pescaloco]

Thanks guys,

Some of the areas are quite large, and this is all outside in the field repair or
finish restoration.

I like the Duratec idea because it lays down nicely (without much orange peel) and thins the mix down to a sprayable consistance with out the negative effects of thinners. I know it gives verly little hide (due to opacity)
but it seems like it might work with a good solid white base of the original gelcoat ??

[rwatson]

gelcoat (can easily be colour matched.

I'd like to see that. Matching gelcoat has never been easy for me, but maybe I dont know the right spells.

[Wynand N]

Rwatson, it is really easy if you put your mind to that;)

This is how we go about it. Firstly, I downloaded a good Java applet that uses primarily 3 colours - red, blue and green. These colours can the be adjusted by dragging the colours scales with the mouse until you have the three colours matched to the pigments you have of the same three colours.
Now it is a matter of overlay them by dragging the colours - however, it take some experimenting with the ratios to get the colour right or very close - takes about 5 minutes for a very close match. Use the same quantities in ratio and mix. If a bit off, one then add a bit of white perhaps for faded gelcoat, or other different colours to the three main red, blue and green mixed. It pays however to know what to add and how colours are changed.

We do this all the time fixing powerboats, canoes etc. Hope this helps.

[rwatson]

Rwatson, it is really easy if you put your mind to that;)

This is how we go about it. Firstly, I downloaded a good Java applet that uses primarily 3 colours - red, blue and green. These colours can the be adjusted by dragging the colours scales with the mouse until you have the three colours matched to the pigments you have of the same three colours.
Now it is a matter of overlay them by dragging the colours - however, it take some experimenting with the ratios to get the colour right or very close - takes about 5 minutes for a very close match. Use the same quantities in ratio and mix. If a bit off, one then add a bit of white perhaps for faded gelcoat, or other different colours to the three main red, blue and green mixed. It pays however to know what to add and how colours are changed.

seee- I *told* you you need magic ... I was right!! And thats assuming you can get the shading right on your monitor

I bet the patch is still easy to see even on a "good" one - am I right :-)

"Any sufficiently advanced technology is indistinguishable from magic. Arthur C. Clarke"

[pescaloco]

Wynand,

that sounds interesting can you tell me where one finds and appelet (I am not super computer savy)

White boats and the thousand shades of white are what I deal with, I do some gelcoat matching pretty good some times and really struggle other times. I used red / sienna / black / yellow / brown or some combination and it can be quite difficult.
Can you tint whites with only primary colors ?? particuarly in "small quantaties" ?

Please tell me about the Java Appelet


Rwatson, it is really easy if you put your mind to that;)

This is how we go about it. Firstly, I downloaded a good Java applet that uses primarily 3 colours - red, blue and green. These colours can the be adjusted by dragging the colours scales with the mouse until you have the three colours matched to the pigments you have of the same three colours.
Now it is a matter of overlay them by dragging the colours - however, it take some experimenting with the ratios to get the colour right or very close - takes about 5 minutes for a very close match. Use the same quantities in ratio and mix. If a bit off, one then add a bit of white perhaps for faded gelcoat, or other different colours to the three main red, blue and green mixed. It pays however to know what to add and how colours are changed.

We do this all the time fixing powerboats, canoes etc. Hope this helps.

[Wynand N]

here is the link for the applet we use. Just drag the colour squares over each other and see what happens. Adjust shades of blue, red and green on the scales to suit - or go about as describe above somewhere. Enjoy:cool:
http://www.lon-capa.org/~mmp/applist/RGBColor/c.htm

[pescaloco]

here is the link for the applet we use. Just drag the colour squares over each other and see what happens. Adjust shades of blue, red and green on the scales to suit - or go about as describe above somewhere. Enjoy:cool:
http://www.lon-capa.org/~mmp/applist/RGBColor/c.htm

Thanks man appreciate it

[rwatson]

here is the link for the applet we use. Just drag the colour squares over each other and see what happens. Adjust shades of blue, red and green on the scales to suit - or go about as describe above somewhere. Enjoy:cool:
http://www.lon-capa.org/~mmp/applist/RGBColor/c.htm

Oooh er - how does that help mixing stuff? It doesnt even show the percentage figures (in precises numbers) of each primary colour.

If you monitor isnt correctly adjusted, the colours themselves are off.

There must be a better way - something commercial like they use at Paint Shops.

[ondarvr]

We use a computer with a color eye similar to a paint store, it needs to be calibrated for the exact pigments being used, plus be recalibrated for each new batch of pigment. There are people that can do it very well by eye, but its almost a lost art.

[Wynand N]

It pays however to know what to add and how colours are changed.


Watson, I never said it is perfect, but take a lot of sweat and guesswork out of it. I will repeat again - first of all get the three main colors adjusted on the slider until it matches your color needed - sometimes you would only need to mix two colors for a match.
However, if you have a match, check and see how your three main pigments compare to the ones on screen and adjust the color intensity of your pigment colors to match. Mix them up and you will have a close to perfect match. If a bit off, adjust the color and read the sentence in the quote above.

Unfortunately, I write this post from my house computer and the applets are not on my bookmarks here, but there is another link we use together with this basic applet mixer that actually shows how colors changes with different colours added and this let you know what to add to get a color darker/lighter or to fade it a bit....
As said, we do repairs of gelcoats quite successfully regularly using this method with the limited amount of color pigments we have.

Remember, necessity is the mother of all invention....