Black blemishes on Fiberglass skin.

[Qwe]

Hi all, my 1998 Aerolite travel trailer has these black (mildew?) spots on its Fiberglass skin. Not as heavy as this example but just as unattractive. It’s most pronounced on the front, back and especially where the roof transitions to the end caps. Can this be restored to original condition? Asking what products and techniques (bristle brush, buffer, elbow grease etc), with/without a hot water pressure washer you’ve used to hopefully restore your RV to its original lustre? Thx and enjoy the day eh?

 

[Boat Bum]

I would first try any number of marine black steak removers, e.g. Star Brite

 

[gwinger]

That appears to be mildew. Looking at the decals and dullness of the finish, it appears like the exterior has been neglected for quite a while.
A good cleaner/wax and lot's of elbow grease may remove most of it.
Or if your up to it, a mild polishing compound and a dual action buffer with the foam pads.
Then a quality wax.

 

[Qwe]

Star Brite black streak remover or mildew remover seems to be their best product for my needs thanks. I see spray 9 is mentioned along with a myriad of products. Can these exterior black streaks, mold and mildew stains be removed with just one product?

 

[Qwe]

I have a buffer and I think using it for stain removal/surface cleaning would do the better job. I’ll Pressure Wash the RV first to lessen the chance of scratches from buffing. Then a quality wax.

 

[gwinger]

Star Brite black streak remover or mildew remover seems to be their best product for my needs thanks. I see spray 9 is mentioned along with a myriad of products. Can these exterior black streaks, mold and mildew stains be removed with just one product?

Black streaks are caused by water runoff from the roof material. Not the same a mold and mildew.
The mildew grows in microscopic pores in the paint.

 

[gwinger]

I have a buffer and I think using it for stain removal/surface cleaning would do the better job. I’ll Pressure Wash the RV first to lessen the chance of scratches from buffing. Then a quality wax.

Make sure the buffer is a low speed dual action with the foam pads. A high speed buffer can actually burn the paint.
I used to detail cars and found out how much damage the high speed buffers and cloth pads will cause.

No need to pressure wash. In fact the pressure washer can and will penetrate the sealant around the windows and trim pieces.
Just a good hand wash will remove the loose stuff.

 

[Qwe]

K, well I’m dealing with mildew primarily here I believe so I’ll research mildew specific cleaners. I’ve been considering Dicor Exterior Wash concentrate but it doesn’t mention mold/black streaks, just dirty surfaces.

 

[gwinger]

Make sure the buffer is a low speed dual action with the foam pads. A high speed buffer can actually burn the paint.

Harbor Freight sells a decent D/A buffer and foam pads. Plus a Mequiares polishing compound.

I used to detail cars and found out how much damage the high speed buffers and cloth pads will cause.

No need to pressure wash. In fact the pressure washer can and will penetrate the sealant around the windows and trim pieces.
Just a good hand wash will remove the loose stuff.

 

[Qwe]

I used my grinder yrs ago & learned that lesson the hard way, lol. It was on a beater Volkswagen but still. And I’m still fixing up “beaters” all these years later but these restoration projects are a great learning. I’m just about done (for now) and it would be great to have all my inside efforts reflected on the outside as well.

 

[Boat Bum]

For the price you're crazy not to try a spray solution before compounding/buffing, it will certainly reduce the effort.

 

[Boat Bum]

As an after thought, try a magic eraser from Mr Clean, it's a cheap investment.

 

[Qwe]

I've come across a couple of products that state no scrubbing at all, just apply, wait 30 seconds & rinse. And I have uses those Mr Clean scrubbies and their frickin amazing actually. I'm gonna try this 1st, great suggestion.

 

[TheBar]

I tried removing black mildew from my RV with an electric buffer and rubbing compound. A lot of work and not good results. I think its too hard on the gelcoat. I've used this Walmart bathroom cleaner with bleach for years for years. Even on my white latex outdoor paint on my house. It has other ingredients and works much better than just a water/bleach mixture.

Spray it on and wait 15 minutes and mostly it disappears by itself or with a wipedown. Don't leave it on any longer than needed. Follow up with a good wash and wax.

Washing every 6 months mostly eliminates needed to use a product like this but life gets in the way sometimes.

 

[Qwe]

Thx for this. The trailers 27 yrs young, was sitting for quite awhile beforeI found it through an estate sale. So I’m not expecting new penny results here but the Fiberglass shell is in great shape, no bulges, delamination, not even stone chips really. First effort begins today w Mr Clean Magic Eraser 2x scrubby tings just to discover what I’m up against.
I’ll keep you all posted, enjoy yer day eh.

 

[Kirk]

With an RV of that age, the gelcoat would be mostly gone, especially with it having been neglected. Even a well-cared for fiberglass RV will slowly lose the gelcoat. If you have mildew it would mostly be where the gelcoat is missing. If you use a polish that has a mild abrasive in it that would make it shine again but it will not last like the original finish does. There are gelcoat repair kits marketed mostly for boats, and I used one on our fulltime class A when it had some spots needing gelcoat repair with good success. That experience was about 15 years ago and I don't remember which product I used. If you choose to do that, it is very important that you get the areas completely clean first and that it has no wax or similar coatings.

 

[Qwe]

Thank you, I’m going to clean a small area thoroughly and go from there.

 

[Qwe]

Well I can’t say enough about these Mr Clean Magic Eraser pads. After washing (hotsy pressure washer) I figured I’d give the nose - area of most mildew - a try whilst it’s still wet.
With next to no effort the mildew/remaining stains rubbed right off. One pad cleaned 1/2 the nose, a quick rinse later and I’m confident I can begin removing the oxidized layer w my buffer. Leaning towards Meguiars M67 as it’s their more aggressive product.
The last thing to determine tho (as suggested in an earlier post) is how much gel coat remaining on this 28 yr old trailer.
How do I determine this and would it make a difference if I simply start removing the oxidation?

 

[Kirk]

when you polish the weathered fiberglass (or paint), it removes the surface. The gel coat is a resin-based finish applied to fiberglass, and it's the primary layer exposed to the elements. Over time, UV radiation from the sun breaks down the gel coat's molecular structure, causing it to become more porous. The gel coat is a resin-based finish applied to fiberglass, and it's the primary layer exposed to the elements. Over time, UV radiation from the sun breaks down the gel coat's molecular structure, causing it to become more porous. While buffing can make the surface shine again, it doesn't replace the missing gel coat. For that reason, the shine will not last as long and more maintenance will be needed. Its a natural aging process but gel coat can be replaced.

 

[Qwe]

Thx for this. Google search says “If you get a white chalky powder off the Fiberglass skin” there’s no gelcoat left. If this is something I can replace myself (cheapy! lol) I’d consider it but it would never be factory.
If I understand the situation then I’ll cut through the oxidation/restore the fiberglass w this Maguires 1Step Compound M67, and seal the results with a quality wax.