DIY molding new boots (liners and shells)

[mntlion]

So just to start off, I DONT work for any boot brands and I have been boot fitting for 20+ years. This is what I have found, you may find different things. This is basic instructions for a DIY liner/shell molding, at home. You don’t have to do this, as the liner will pack out anyways, with a bit of time

Few basic points:

So ALL liners and ALL shells are moldable. IT doesn't matter if the brand markets the boot this way, bottom line it will and can be stretched. The liners all will stretch out a bit after 5-10 days of wearing them and the shells CAN all be stretched. If you don’t heat mold them, that is fine, but after 10 days this method won’t really won’t change the boot much

To change a boot (liner or shell) you need both heat and pressure. If you only heat a boot and don’t stretch it, it won’t change much. If you stretch a boot, that is not heated, it will go back to its original shape as well. You need both to make a permanent change


This procedure is useful you have a new tight boot, that you just can’t ski as it is. Best way is still just to go ski the boot for a few days.

you will need

a tub/pot of hot water, big enough to place the boot shell in 20cm deep.
some way to heat the liner up. I use a convection oven at home, but a hair dryer will work if you are careful, or “intuition bag of rice” as well
some thicker socks
some padding that is 3mm thick when compressed (cheap blue camping foam works)
toe caps (the cut off end of a thick sock works)
beer


1) Add padding to the bare foot, everywhere you want more room created. Width, instep, strange heel spur, what ever. then Add a toe cap over this.
2) put on the thick sock over all this. yes you foot will now be 1 size bigger (remember when we talked about change happens with heat and pressure. This is the part that creates the pressure)
3) stand the boot shell in the very hot water, and let it fill up as well. Should be hot enough that you don’t burn your hand, but you don’t want to keep it in the water for more then 1-2 seconds
4) Heat up the liner, 175 oven for 5-10 min. or heat the inside of the liner with the blow dryer. You want the liner to become soft, warm and a bit puffy. Or google intuition liners rice heating. (remember when we talked about change happens with heat and pressure. This is the part that creates the heat)
5) remove the liner from the heat, and stuff your foot in. Yes it is tight, good. Wiggle your heel around to make sure the heel is both down and back all the way.
6) remove the shell from the hot water, and open the lower cuff open wide and stuff your foot into this. Yes its tight. Again wiggle your heel around, also pulling up on the liner to remove any wrinkles that might happen with stuffing the liner into the shell
7) buckle lightly, flex, make sure it feel tight, but OK
8) bucket the boots to the max, yes, I know it tight. Suck it up princess. No do it up one notch tighter then that. Yes. max the buckles out tight.
9) open beer, and wait for 10 minutes for them to cool. If you can go outside and stick them in a snow bank to help cool them. Enjoy the numbing of the beer, and as your foot falls asleep.
10) after 10-15 min, remove the boot, remove all the padding, let your foot come back to life and then put on a thin sock and try the boots on again. and be amazing on how much more room them have.

[swissiphic]

Thanks for the info mntlion. Coupla questions though...
--- can you use a convection oven for the shell bake? If so, what temp/how long? Would bake temp and time vary for different plastic chemistries and special features like rubber soles and/or dynafit binding metal inserts?
on that note....
--- is it safe to mold ski touring boot shells with rubber soles and dynafit inserts; will the metal/plastic bond/integration be compromised at all?

Might give 'er a go with some old shelved touring boots used for experiments.

[mntlion]

--- can you use a convection oven for the shell bake? If so, what temp/how long? Would bake temp and time vary for different plastic chemistries and special features like rubber soles and/or dynafit binding metal inserts?
on that note....

water is a very even heat source and can't damage parts, and easy to make/find. Just use that. MUCH safer then oven.

--- is it safe to mold ski touring boot shells with rubber soles and dynafit inserts; will the metal/plastic bond/integration be compromised at all?

I have never had an issue and have done this with bigger alpine shells that tour (K2, technica) and little light weight rando slippers too.

If you are scared DONT do it.

if you ar not sure, go lighter with the heat,

but at the lower temps I'm using and buckles vs foot pressure, it would be REALLY hard to fuck something up

[hutash]

Seems like good advice, but the most important question is...what type of beer?

My guess is something with a high alcohol content because this all seems pretty painful��

[mntlion]

Seems like good advice, but the most important question is...what type of beer?

My guess is something with a high alcohol content because this all seems pretty painful��

it ain't comfortable, but with a race (4-8mm) shell fit, I can reduce my boot fitting work by 50-80%

I like "dark and interesting" for beer

[reckless toboggan]

Excellent thread and step by step.

Thanks for posting.

3) stand the boot shell in the very hot water, and let it fill up as well. Should be hot enough that you don’t burn your hand, but you don’t want to keep it in the water for more then 1-2 seconds

Do you know what temp range this is in C?
Do you use hot tap water?
Or heat in a kettle, or some such?

[mntlion]

Excellent thread and step by step.

Thanks for posting.


Do you know what temp range this is in C?
Do you use hot tap water?
Or heat in a kettle, or some such?

I'll measure my water bath at work. 70-80'C is a guess

boil water (kettle, stove, etc)

[Beder]

Here's another way which I've done successfully with Salomon X Pro and Quest Max boots.

pad foot where you need room
add a toe cap made from old wool sock, then pull on ski sock
heat standard oven to 210 F
place shell only in oven for 10 minutes (lay shell on wood blocks, not on metal rack)
after 10 minutes remove shell, add liner, put foot in boot and buckle up
drink your beer indoors for 10 minutes then go stand in snow for another 10
wahlah done

Again I've done this with Salomon boots. There's a youtube vid with two German speaking lads showing this very technique

[cat in january]

Followed Marshall's advice on the board a few times over the years. He used steam and a bit longer followed by ice bath to fix. I have a large pot my boot soles catch on the ends and the boot hangs upside down. Heat to boiling, hang boot, prep foot with tape and cotton balls, sock, liner, fill bucket large enough to hold boot with ice water. Buckle up super tight making sure liner is pulled up and heel is snug. Stand level for 5 minutes in ice water. Repeat with other boot.

My experience is limited to 2 boots. I "think" a great deal of the molding is actually the hot shell molding the outside of the liner (I use the turkey bag with boiling salt water technique to mold liners) and maybe a bit of the shell. Felt better about boot fit afterwards and did not notice any negative affects to boots. Boots were Lange RS with PU plastic and Dynafit Zzero with PB plastic. Still holding off on heat molding some tlt5 as I do not have a mission for them.

[gregL]

Several classes I've attended at Masterfit have advised against using hot water on ski boot shells, citing articles by Martino Colonna (plastics expert and adviser to multiple ski boot manufacturers). Depending on the plastic, hot water will degrade the chemical structure of the boot, making it permanently softer.

"Hydrolytic stability is also a major issue for some plastics. Hydrolysis is a reaction between water
and polar groups such as esters, urethanes and amides (Figure 21) [65]. Hydrolysis causes the cleavage
of the polymer backbone and the consequent molecular weight decrease. Since polyolefines do not
contain polar groups that can be hydrolyzed, normally do not suffer of this problem [65]. For the same
reason ether based polyurethanes suffer from less hydrolysis with respect to ester based polyurethanes.
Hydrolysis is accelerated by temperature and, of course, by humidity. Soaking the boot in hot water for
boot-fitting purposes should be avoided. The effect of degradation on plastics used for ski-boots has
been reported from Parisotto et al. [58] by means of DMTA analysis of two Pebax samples before and
after degradation in hot steam. The results obtained (Figure 22) show a decreased modulus after
degradation that can be ascribed to the decreased molecular weight due to hydrolysis and/or to water
absorption. On the basis of these data it is clear the importance to store ski-boots in a dry ambient,
especially if they are made of TPU, Pebax or Nylon. "

Full article here: www.mdpi.com/2075-4663/1/4/78/pdf

[cat in january]

Trust GregL and not me. Thought I had heard something about that. Last time I did it zipfit still had a video showing the steam technique for shells.

[swissiphic]

Several classes I've attended at Masterfit have advised against using hot water on ski boot shells, citing articles by Martino Colonna (plastics expert and adviser to multiple ski boot manufacturers). Depending on the plastic, hot water will degrade the chemical structure of the boot, making it permanently softer.

I've also read about that potential result and was gonna comment but couldn't find the reference.

I also recall the effect of free water/ambient air humidity being absorbed somehow by ski boot plastic and altering shell stiffness at warmer temps...can't really understand how that works but it was in some official ski boot plastic technical papers so must be a real phenomenon.

However
I also read about a solution to the direct hot water to ski boot shell problem.

Use sealed/waterproof turkey cooking bags. Place boot shell into turkey bag and then another turkey bag INTO the shell. place unit into boiling water then fill the turkey bag in the inside of shell with boiling/hot water so that both inside and outside of shell is heated at same temp of water.

This way, there is no direct contact of the h20 with the shell plastic and the chemical process of softening is mitigated.

Or at least that's what i recall. What do you think, Greg? Viable solution?

[gregL]

What do you think, Greg?

Could work. However, the optimal temperature for modifying a ski boot varies from around 240 F. (softer Grilamids) to around 300 F. or above (race boot polyethers), and the temperature of unpressurized boiling water is 212 F.

Since I've cooked hundreds of boots in the convection oven without a fatality, I tend to favor that approach.

[swissiphic]

Could work. However, the optimal temperature for modifying a ski boot varies from around 240 F. (softer Grilamids) to around 300 F. or above (race boot polyethers), and the temperature of unpressurized boiling water is 212 F.

Since I've cooked hundreds of boots in the convection oven without a fatality, I tend to favor that approach.

okay, very good to know...as that was part of my o.g. question on this thread.

Any clue specifically with the dynafit vulcan shell; what temp and how long in a convection oven?

[GoldenBC]

Having heat molded many of my own shells, I can't really recommend it. The general relaxing the shell does around your ankle tends to ruin any good hold the shell may have originally had. As well, if you crank the buckles when the boot is extremely soft, it is very easy to distort the shell on or around the buckles.

[Nevada29er]

I've used the steam heating method on a few pairs and not noticed any ill effects (i.e. softening). Maybe its very subtle? Worth noting that I didn't crank the buckles, as that could distort the shell.

[slashy]

just as a spin on this:

when being fitted a pair of kryptons years ago in Chamonix following procedure was done : first mold the liners. go ski a few days. then the shell needed to be stretched (toe area mainly, because 1 foot is 5-6 mm longer than the other one) : shell was cooked in the convection oven and a traditional liner from a random pair of boots (same mondosize) was put on my long foot, padded and then used to make room to the shell, this in order not to abuse/deform my proper liners. Plake was there also fitting boots for himself and he endorsed this method (he was still on dalbello then). he mentioned a shell could be stretched a full mondo point with this method.

since it is so long ago i cannot really remember, but either my own liner was heated once more locally in the toe area with a blower or either it was heated entirely to conform to the added room in the toe area

[gregL]

Any clue specifically with the dynafit vulcan shell; what temp and how long in a convection oven?

I would do Vulcans/Mercurys for 9-10 minutes in a shop oven (usual temp is somewhere between 235 and 250 F. - ours are supplied by Salomon and K2 but are the same model oven - but if you are home cooking I'd suggest checking with a thermometer first). If you don't have convection I would preheat to 250 F. and turn it off before you put in the boots. Don't expect a drastic change with a Vulcan in terms of width, but it does create some more instep height.

(edit because I misspelled Salomon and I know they read this forum regularly)

[gregL]

I would do Vulcans/Mercurys for 9-10 minutes in a shop oven (usual temp is somewhere between 235 and 250 F. - ours are supplied by Salomon and K2 but are the same model oven - but if you are home cooking I'd suggest checking with a thermometer first). If you don't have convection I would preheat to 250 F. and turn it off before you put in the boots. Don't expect a drastic change with a Vulcan in terms of width, but it does create some more instep height.

PS We have 3 ovens and they all run at slightly different temperatures, so best to set your home oven at 225 F. first and measure the temp, then adjust as needed to get to 235-240 F. (113-114 C.) . . . (the shop ovens have a fixed temperature but they seem to change a little over time).

[swissiphic]

PS We have 3 ovens and they all run at slightly different temperatures, so best to set your home oven at 225 F. first and measure the temp, then adjust as needed to get to 235-240 F. (113-114 C.) . . . (the shop ovens have a fixed temperature but they seem to change a little over time).

Thanks Greg! Have convection oven and a separate oven thermometer to confirm correct temp. Learned that lesson the hard way after melting one of two intuition liners in one pair. lol. At least I didn't melt one of two vulcan shells. Yet.

[margotron]

Good info. Have been meaning to do this

[mntlion]

bump

[Judo Chop!]

So a couple weeks ago my shells were apparently too close to the passenger side foot vents in my truck pumping hot air for 40mins before skiing. I usually leave my liners (zipfits) there to warm up a bit but not the shells, and not this warm. Felt fine skiing that day but...
Ever since then they’ve been looser around the ankle, which is not ideal. I hate packing in extra foam or cork to a liner. Never as good as shellfit.
Am I fucked? Anything I can do to bring back the shells a bit?

Lange xt130 FT for what it’s worth.

[swissiphic]

Judo Chop: Not a real bootfitter so hopefully someone with some pro chops can weigh in on this one ...but...I do recall talkin' to a guy about 'reverse punching' ankle and shafts of ski boots to compress the plastic and form it around skinny ankles/lower legs, etc... don't know anything about the techniques involved. The guy might have said he did it by hand and just squeezed/pushed on the plastic but not sure... it was a few decades ago.

[Judo Chop!]

^that would be amazing if possible. Never heard of it but I always wondered why nobody had tried. Well.. I guess fischer does.

Hopefully someone knows more???