# Yellowing GRP



## danny13 (Nov 10, 2011)

The GRP on my motorhome seems to have yellowed quite a lot, is this just what happens with age (its 11 years old)?

Can anything be done to renovate/whiten the finish?


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## rotorywing (Jul 19, 2010)

Could try this
http://www.force4.co.uk/8595/Farecla-Marine-Professional-Surface-Restorer.html

or 
http://www.force4.co.uk/3134/Starbrite-Hull-Cleaner.html


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## ned (Dec 12, 2006)

*yellowing*

Hi 
I go along with rotorywing. Just purchased a Hymer s 650 with the whole of the out side 'chalked up' and looking decidedly worst for wear. There was yellowing around the headlights and tight radii on the GRP panels. I am now into my third day with the farecla No 3 compound paste followed by the Ferecla No 10 finishing compound. I have chosen to do it by hand because the gel coat is likely to be a bit thinner than marine gelcoats. Use plenty of water as you do it from an old water or garden spray bottle. Vary circular and opposite directional motions to spread the wear across the surface. I did finish up buffing first by hand and then using a light touch with an automative polisher at a very slow speed. Result...................... Fantastic. Right back to its original deep gloss. Don't use this stuff on sprayed ali panels...... Too coarse!!!!

I shall finish of with the new Mer polish with wax otherwise it will just go chalky again.

God my arm aches :roll: :roll: :roll: :roll:

Ned


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## hogan (Oct 31, 2006)

Usual cause for gel coat going yellow is that it has been cleaned with jif. 
A big no no.


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## H1-GBV (Feb 28, 2006)

hogan said:


> Usual cause for gel coat going yellow is that it has been cleaned with jif.
> A big no no.


OOPS!  I did the offside of the MH with Mer and used some Tesco Cream Cleaner to bring the plastic vent covers towards whiteness. Next day I did all the nearside then went to get the Cream Cleaner to do the water inlet & electric inlet. Found the bottle of Mer! 

A very thorough soaking with water and a "scrub" with the brush on a lance, then another go with elbow grease and Mer. Fingers crossed.

You live and learn - Gordon


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## richardjames (Feb 1, 2006)

I use mer to cleanup the GRP bits - does a good job


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## Jezport (Jun 19, 2008)

Most gelcoat yellowing is caused by UV damage. Most modern jif, cif cleaners are water based and will not damage gelcoat. It may dull it by abrading the surface.


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## danny13 (Nov 10, 2011)

Jezport said:


> Most gelcoat yellowing is caused by UV damage. Most modern jif, cif cleaners are water based and will not damage gelcoat. It may dull it by abrading the surface.


I also thought it was likely to be UV damage, can this be improved using some of these marine cleaners/restorers or am I likely to be wasting my money on them? It sounds like the UV may have actually damaged the paint below the gelcoat?


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## WildThingsKev (Dec 29, 2009)

Farecla also produce an "Ultimate UV Wax" which I'm now using after giving the van a superfine compound. It does seem to hold off the dulling of the grp a lot longer than anything else I've tried.


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## Jezport (Jun 19, 2008)

danny13 said:


> Jezport said:
> 
> 
> > Most gelcoat yellowing is caused by UV damage. Most modern jif, cif cleaners are water based and will not damage gelcoat. It may dull it by abrading the surface.
> ...


Not usually repairable although a good polish will remove any surface damage. But most gelcoat is so thin that the yellow is likely to bee too deep to remove.


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## Jean-Luc (Jul 21, 2005)

danny13 said:


> ............... It sounds like the UV may have actually damaged the paint below the gelcoat?


Gelcoat itself holds the colour, there would be no paint involved.
I use marine products to remove any oxidation and discolouration on the gelcoat on my Rapido


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## danny13 (Nov 10, 2011)

Here are some (poorly lit) photos of what I'm working with.....the whiter area is are where the previous owner roller painted the GRP with household gloss! Quite a contrast in colour!


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## WildThingsKev (Dec 29, 2009)

Are you certain that the yellow is not also a layer of paint.


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## danny13 (Nov 10, 2011)

Pretty sure its not, nitromors bubbled through the top layer of gloss then I wiped it off the yellow below has a very smooth surface, not like paint, I might leave the nitormors on a little longer to double check on a test patch somewhere. I think its just a very badly faded GRP.


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## rogerblack (May 1, 2005)

See this posting:

http://www.motorhomefacts.com/ftopicp-1151457.html#1151457


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