chemical removal of yellowing white gel ?

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.

Originally Posted by Fanie

I zoomed it, rotated it, fade in, fade out, with and without glasses, with the microscope, one eye, the quick look, the stare... 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]

Originally Posted by ondarvr

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]

Originally Posted by 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.

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]

Originally Posted by Wynand N

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]

Originally Posted by 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.

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

Originally Posted by 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.

[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
http://www.lon-capa.org/~mmp/applist/RGBColor/c.htm

[pescaloco]

Originally Posted by 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
http://www.lon-capa.org/~mmp/applist/RGBColor/c.htm

Thanks man appreciate it