What's happening here? clamp stains

[Justin P.]

Have a small side project going, Mini Mamoli Brittania and for about a week I had the solid hull clamped into a rubber gripped Dremel vice while laying down the deck planking.  Pulled it out today and to my suprise there is a darkening of the wood where the clamp comes into contact with the hull...    No moisture in the shop, the wood has sat for at least several years drying...   cant figure out what would cause the discoloration, wasn't clamped all that tightly...  

 

Just curious.  Explain like I'm five...

[grsjax]

Could be discoloration from the rubber jaws.  Another possibility is moisture.  All air has some moisture and space between the jaws and the hull would be a place that you might get some minor condensation.  If the marks disappear after a few days that is probably the answer.

[Charter33]

Just another thought - was the hull in direct sunlight while in the clamps? It's surprising how quickly some timbers change colour, lighter or darker, when exposed to daylight. 

[MEDDO]

My wild guess is that the rubber being some type of petroleum product is not really inert and somehow it is either reacting with the wood or releasing some type of oil/residue onto the surface it's clamped onto.   I've seen this type of thing happen with a couple other items I have that were clamped or sitting on rubber bases on a table or something. 

[Charter33]

Another thought - your clamp looks pretty new, and the jaws appear to have been injection-moulded. Another possibility could be that there is still some residue of the 'releasing agent' from this manufacturing process on the jaws. I have a feeling that the agent is silicon based, but I could be wrong. Light sanding ought to get rid of it. Good luck!

[xken]

Others have identified the possible issue being the rubber jaw inserts. A couple of points to consider next time remove the rubber inserts since you are clamping and a portion of your clamping force is lost in the rubber; and use scrap wood of the same kind being clamped between the jaws and wood being clamped. Jaws or a harder wood could leave impressions in the wood as well. I suspect what you are seeing is mold release(silicone based) that is used in the production process. Try cleaning with acetone and then light sanding after the acetone has dried completely. This is just one of the many "Joys" of model making. 

[Justin P.]

1 hour ago, xken said:

Others have identified the possible issue being the rubber jaw inserts. A couple of points to consider next time remove the rubber inserts since you are clamping and a portion of your clamping force is lost in the rubber; and use scrap wood of the same kind being clamped between the jaws and wood being clamped. Jaws or a harder wood could leave impressions in the wood as well. I suspect what you are seeing is mold release(silicone based) that is used in the production process. Try cleaning with acetone and then light sanding after the acetone has dried completely. This is just one of the many "Joys" of model making. 

 

 

Do you mean mold release from the wood or the rubber?   Here is another view...

[Charter33]

The jaws were made by injecting heat softened rubberized plastic into a metal female mould sometimes called a 'die'. Once the material has cooled it hardens and the die is opened so the product, in this case the jaw, can be removed. To help get this item out the inner polished surface of the die is first sprayed with a fine mist of 'releasing agent' that helps prevent the liquid plastic from sticking to the metal. It's the remnants of this spray that might have caused the discoloring of the wood.

[xken]

You can wipe both the wood and the rubber clamping faces with acetone. The wood can be lightly sanded as well.