MVm

Wet Molding Leather: First Pulls, and Questions

6 posts in this topic

Hi there, everyone, 

I recently completed my first mold, made to form a simple rectangle with radiused corners out of 8oz. veg. tanned leather, and have some questions concerning how to improve the process. 

For starters, I'd like to adjust the mold. The mold base and presser piece are a mix of CNC'd plywood, and stacked laser cut MDF pieces. I've attached a section view of the mold. Do I need to include the lower radius on the buck--beyond the leather--or would it be best to minimize or eliminate it altogether? My reasoning was that it would help spread out the leather while pressed, but I'm a novice at this sort of thing!

mold_section.png

 

When designing the mold, I left hardly any clearance for the leather/buck/presser piece. This tight tolerance made it rather difficult to press. Additionally, I neglected to seal the plywood buck, and noticed that the individual ply layers were pressed into the leather. The ply was sanded smooth before use, so I assume that the individual ply layers swelled, creating these distinct layers. My guess is that a combination of the untreated wood and tight fit led to this pattern. I've attached a picture showing one of the corners, with the plywood pattern. 

plywood creep.jpg

I plan on adding some clearance between the buck and presser piece; would 1/16" be sufficient? 1/8"? 

From now on, these molds will be sealed with clear urethane. Is there something better to use for this purpose? 

One last thing-- my second and third pulls show a bit of a curve around the edges of the leather, bowing inwards. It's more pronounced in the photo, but it's there nonetheless. My process for the three is below:

  • #1 - Soaked in cool water for 20 minutes, pressed, left to dry in mold for 2 days
  • #2 - Soaked in cool water ~5 minutes, dipped in hot water for ~30 seconds. Left to dry in mold for ~24 hours.
  • #3 - Soaked in cool water ~10 minutes, dipped in warm water for 1 minute. Left to dry in mold for ~24 hours.

Could this bow be caused by pulling the leather too soon? Or, could it be something else entirely?

bowed edges.jpg

 

Any help is greatly appreciated!

Edited by MVm

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I don't have any help to offer, but I think those turned out really cool.

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Plywood and water don't mix well from my experience. Seen a few things made with molds and it seems most people just use solid pieces of hardwood. That's all I got.

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Like Mattsbagger said, . . . nix on the plywood.

All my molds are generally southern white pine (cut out of left over 2 x 12's from building projects).  There is an occasional white pine piece from a 1 x 6, . . . 

I don't have any problems with any of the stuff they turn out.

The "clearance" you spoke of needs to be a tad more than the leather you are molding, . . . otherwise you compress the leather, . . . 

May God bless,

Dwight

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just my opin, but I think I you chose to you could use tepid temp water instead of the 2 different temps for the wetting of the leather, and if you are cncing plywood and have something else you can chose from, Delran plastic.  the Delran would not need to be sealed and would last a long, long time or even nylon, the molds look good regardless, what are you making cases for? 

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13 hours ago, bikermutt07 said:

I don't have any help to offer, but I think those turned out really cool.

Thanks, bikermutt07! I think it's a good start. 

12 hours ago, Mattsbagger said:

Plywood and water don't mix well from my experience. Seen a few things made with molds and it seems most people just use solid pieces of hardwood. That's all I got.

 

9 hours ago, Dwight said:

Like Mattsbagger said, . . . nix on the plywood.

All my molds are generally southern white pine (cut out of left over 2 x 12's from building projects).  There is an occasional white pine piece from a 1 x 6, . . . 

I don't have any problems with any of the stuff they turn out.

The "clearance" you spoke of needs to be a tad more than the leather you are molding, . . . otherwise you compress the leather, . . . 

May God bless,

Dwight

Appreciate it, Dwight and Mattsbagger. I'm definitely going to move away from plywood/MDF, and give the leather a little more room in the press!

5 hours ago, OLDNSLOW said:

just my opin, but I think I you chose to you could use tepid temp water instead of the 2 different temps for the wetting of the leather, and if you are cncing plywood and have something else you can chose from, Delran plastic.  the Delran would not need to be sealed and would last a long, long time or even nylon, the molds look good regardless, what are you making cases for? 

Good call on simplifying the wetting, OLDNSLOW; I don't know what I'm doing there, and it's ended up being an additional step with ambiguous results (largely due to my inexperience).

Switching to a synthetic is an interesting idea. I'll be trying a Delrin mold soon!

Edited by MVm

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