Romoving Tree sap

[XLD]

My boat roof is full of tree sap all if a sudden. Not sure which tree but it looks like thousands of rust specks and they are proving stubborn to remove. 

What cleaner can anyone recommend?

[MtB]

25 minutes ago, XLD said:

My boat roof is full of tree sap all if a sudden. Not sure which tree but it looks like thousands of rust specks and they are proving stubborn to remove. 

What cleaner can anyone recommend?

 

I've heard that HOT water dissolves it better than cold. 

 

(Hand-warm works fine on my boat)

[Tony Brooks]

I think it is honeydew dropped by aphids feeding on the tree. A Mike says, how water probably better than cold plus some boat shampoo.

[tree monkey]

If it's honeydew, which is likely, it is primarily sugar so anything that will shift sugar should work

[XLD]

Tried BOILING water. No effect! Bleach next!

 

[Tony Brooks]

13 minutes ago, XLD said:

Tried BOILING water. No effect! Bleach next!

 

 

Did you put some boat shampoo or even washing up liquid in the boiling water, and did you use a scrubbing brush or deck scrubber?

 

Are you by any chance near anyone doing metal grinding or a railway line. I am thinking steel dust stuck in whatever came down from the tree and rusting, discolouring the paint.

 

[Ronaldo47]

Resinous tree sap is best removed with a natural solvent such as genuine turpentine.  Much more effective than white spirit or turps substitute. Genuine turpentine can be difficult to find in shops, other than those that sell artists' supplies, which sometimes have highly refined stuff in small and expensive bottles. I had to get my last supply on-line.

[Quatre_Bougies]

Baby oil wipes or the baby oil on a rag.  Works brilliant for any sticky residue.

[LadyG]

23 hours ago, XLD said:

My boat roof is full of tree sap all if a sudden. Not sure which tree but it looks like thousands of rust specks and they are proving stubborn to remove. 

What cleaner can anyone recommend?

Sugar soap. I spray on and brush  / sponge off with a bucket of warm water,  dont dump the dirty water in the canal.

Bleach is usefull if the black is organic mould. 4fl oz to one gallon of warm water is ideal, try using your wash up brush for scrubbing in corners. Do not use neat bleach, it's fairly hazardous.

Edited August 2, 2025 by LadyG

[MtB]

13 hours ago, XLD said:

My boat roof is full of tree sap all if a sudden. Not sure which tree but it looks like thousands of rust specks

 

 

How do you know it is tree sap and not actually the thousands of rust specks it looks like?

 

[Tony Brooks]

7 hours ago, MtB said:

 

 

How do you know it is tree sap and not actually the thousands of rust specks it looks like?

 

 

That was my thought when I asked about metal grinding and railways. If steel particles land on paint and rust, they can stain the paint because paint is slightly porous.

[fretman]

warm soapy water

[LadyG]

If it turns out to be iron filings, I would get to work with wet and dry, make sure it's properly clean before painting the whole thing.

[Stroudwater1]

On 01/08/2025 at 19:44, Ronaldo47 said:

Resinous tree sap is best removed with a natural solvent such as genuine turpentine.  Much more effective than white spirit or turps substitute. Genuine turpentine can be difficult to find in shops, other than those that sell artists' supplies, which sometimes have highly refined stuff in small and expensive bottles. I had to get my last supply on-line.

It sounds unlikely to be that though as not usually a rusty colour? We sometimes park the car by a cedar tree that drops up to 1/2 inch blobs of this resin. Hand car wash people couldn’t remove it.
 

The only other stuff that works on these lumps  we found is standard purple meths. Takes a while and it’s much the best to get off soon after the clear lump appears. Even if left for ages it eventually dissolves with meths soaked into a paper towel. 
 

For the OP agree with others it sounds like someone nearby has been grinding stuff. A nearby boat in our marina had a coarse sanding disk taken off to the roof of their boat to remove the rust and paint. The fine paint mixed with steel settled on the other boats roofs . It washed off with rain leaving these fine specks of rust everywhere. The specks went after a few months of rain and occasional wash with warm water and shampoo.
 

Mysteriously their boat disappeared from the marina a short time later. 

[XLD]

It's definitely not grindings.