Discolored gelcoat repairs

[John Noland]

Four years after having some blisters and gelcoat problems repaired professionally, the repaired areas are beginning to get a reddish tint. They were perfect matches at first. Does anyone know why the gelcoat gets a reddish tint, and if there is anything I can do to halt further discoloring?

 

[MIke D]

Oxidation

Johm,I asked the same question at our marina. They said that gelcoat repairs are "paint matched" color over the fiberglass repair. They suggested some light compounding to remove the surface change in color.Maybe you can try a small spot?I would be interested to know how you make out and good luckMike D

 

[Jim Willis]

Its selective fading of some of the pigments?

You did not say what color the gelcoat was.However, if it is anyinthing other than black or stark white, the color is tinted with different colors. For instance a cream color will have some added "brown" which is inteslf a mixture of pigments containing red (a primary color).Probably the other pigments have faded and not the red. However- its usually the other way round and red fades faster tham most other primary colors. Color matching etc is described under Fiberglass Trilogy !! in the gelcaot and Plastics forum on this site.However, if it is caused by pigment fading, it might be OK and light compounding might work. This is certainly tru of some red colored gelcoats where the outer layer fades to an orange color than can be compounded off.If the original repair was better blended and the pigments were of higher quality then the problem might not have occurred. Another possibility is that the original gelcoat has become lighter ThanksJim W

 

[John Noland]

Color is Hunter whitem - gone reddish

The color is your basic Hunter white, which is a stark white with the smallest iota of brown & yellow. Fading, while a excellent possible diagnosis, is not the issue. The color has gone from white to a reddish/yellowish white. Is it possible you think that inferior materials might have been used for these particular (professional) repairs? Other gelcoat repairs made to the boat have held up nicely.

 

[Jim Willis]

Other possibilities

They are:1. the gelcoat used in the repair is (as you suggest) substandard in some way so that it has become discolored in some obscure way. I know that old vinyl does this as it oxidises, goes brown, then when you clean it with solvent or IG it goes pink before it is fixed.2. I have heard of gelcoat being discolored when using rubbing compound that has a red or orange dye in it. This usually happens only on severely oxidized (porous) gelcoat but it is a possibiltiy.As a suggestion, I would try to abrade the surface slightly (use a 3M "synthetic steel wool- 000 grade) and see if it looks Ok underneath.A little sea glwo might whiten it enough to match the surrounding area.However I think that the only real way is to redo those areas with fresh gelcoat and do a good job of blending the repair so that you cannot see just where it begins.Difficult without seeing the repair and doing the tests though.ThanksJim W