The Bitumen Experiment

[mtaylor]

AlexBeranov and Garward also use the bitumen so you might have a look that their logs.

[Gaetan Bordeleau]

Captain Steve,

 

What is pleasant with these mixes, everyone can create a mix which suits his needs. I do not follow any ratios. I add bitumen till I am satisfied with the result on a test piece of wood.

 

In this case, 3 ingredients are involved; bitumen, tung oil and turpentine.

Bitumen and tung oil can be mixed together but it is easier if turpentine is used first to help to dissolve the bitumen.

 

Bitumen can be applied with or without the tung oil together or separately. Again,  testing is the answer.

 

When possible, I prefer 1 coat of tung oil. I have never tried by example 10 coats, but I suspect that there woul be a kind of brilliant finish with a certain thickness. Also I think that this finish could be  reflective to the camera flash. I prefer the look of 1 coat, because it has a more natural look without this plastic finish. This reflective surface was particuliary true with linseed oil teck oil which, I guess, are not as refine.

 

Chris,

 

when you say that it sort of acts like a wash in oil painting  this is true especially for the first coat but not so  true for the second coat depending of the drying tie between the 2 coats.

[ChrisLBren]

Hey Gaetan 

 

For me the trick of applying pure tung is to cut the first coat 50/50 with mineral spirits and then apply a second coat at full strength 24 hours later.  I found that the thinned first coat insured even absorption of the second coat.  Also much less seepage which is a tendency of pure tung. 

 

I am using Bitumen patina (which is a liquid) sold by art stores in Europe.  It sounds like you are using the solid form of Bitumen.  As far as the bitumen mix I've only used one coat thinned 50/50 with spirits after the tung is fully cured (a few days later) and it did go on like a wash.  I haven't attempted a second bitumen coat - I'm sure the ageing effect would be more pronounced.  

 

I am curious to see how the effect would change if mixed it directly in the tung oil instead of used as a top coat.  Ill have to try that one !

Chris

Edited October 17, 2014 by ChrisLBren

[Gaetan Bordeleau]

Hi Chris,

 

there are definitely not only one way to apply it.

Yes I use it as a powder, I did not  know it was sold as a liquid also.

[Bill Hime]

To All;

I know this topic is a few years old, but what a great exchange of information! Thank you to ChrisLBren for starting it and maintaining the decorum that one should always expect at MSW!

 

 

Sincere Regards,

 

Bill

[knightyo]

I'd love to see more discussion on this topic!  I'm considering the liquid Bitumen approach... Not sure where to get it in US tho...  I do see Pentart Liquid Patina in the UK tho...

 

Alan

[mitbok]

Pentart Liquid Patina is great, unfortunately it is sold out on Ebay. So far don't see any reliable source in the US.

As mentioned before Bitumen liquids are not finishing products as oils and dyes (use it as a stain on bare wood and you get an ugly, patchy black rotten wood look). Can't just be applied evenly and let dry. Use it as a wash to weather the finished surface (not just wood) to highlight the details, applying small quantities and letting the liquid flow into crevices. Or apply liberally but wipe off the excess on raised surfaces to give it a look of centuries ald object which accumulated dirt over the years. All together it takes the model into a certain style category of fake antiques and is absolutely not necessary as one can build a model in style of Syren Ship model prototypes. Those grimey museum models where just as clean as Chuck's models when they were initially built. On the picture is my 4 oared Yal in progress. Pear with homemade stain before and after applying  Liquid Patina

 

 

Edited November 11, 2019 by mitbok

[druxey]

I've seen paintings on copper where the dark (bituminous) background and any paint that had it mixed in simply craze into flakes and fall off, gesso ground included.

[ChrisLBren]

Frankly I think using a Oil paint Sepia wash would probably do the same thing from my experience dabbling in Oil Painting.  

[knightyo]

To resurrect this one a bit...   What grit do you guys think planks should be sanded down to before tung oil, pentart mix, bitumen, etc are applied?

 

Alan

[grsjax]

Depends on the scale.  For small scales I go down to 320.  Larger scales I use 240.

[vaddoc]

I go up to 400 for no reason at all, just because I like the feel of the wood. Or use 0000 steel wool which I think is equivalent grit. If the wood is to be painted, I like it very smooth. But even 240 is probably ok.

[knightyo]

Below is a pic of an experiment I ran on my swiss pear.  The left column is just unfinished, the middle column is pear with Formby's Tung Oil Finish (which I learned isn't actually Tung Oil), and in the right column are pieces which had Pentart Patina liquid (50/50 mix of mineral spirits/Pentart) applied over the top of dried Formby's.   I'm going to keep experimenting to see if I can get something between the middle and right columns.  Maybe starting out with a 90/10 mix of mineral spirits/Pentart; it was surprising how dark and strong that medium was.

 

I'd love input on the combination of these two products or similar products, as stains/finishes is an area in which I have the least amount of knowledge.  Will these products react with one another over time?  Should either one not be used to begin with?

 

My goal is to reproduce a fairly "aged" look to swiss pear with a finish that will last a long time.

 

Alan