White Board

"So. What's this surprise? And why do you need to know my favourite mathematical derivation?

Sheldon sat on her bed, his eyes closed.

From the bathroom Penny's voice calls "If I told you it wouldn't be a surprise! I gave you the required 3 day advance warning form and everything, so relax and trust me, you'll enjoy it . Just think of it as a special Thank you for not weirding my father out too much"

With his eyes closed, Sheldon has to rely on his other senses. Luckily, they're as acute as his vision so he hears the pad of her bare feet on the carpet, catches the rustle of cloth and the scent of talc. He hears her mutter and struggle with something that rattles metal on wood, then she closed the bedroom door with another rattle of metal.

"Open your eyes, Sir".

He opens his eyes to find her standing in front of him, grinning. She's wearing a long white scientist Lab coat, buttoned shut up the front that covers her from neck to knee. Her hair is pulled back into a tight pony tail and she has Safety goggles up on her forehead. Under the edge of the coat he can see she's just wearing white stockings and white leather cuffs are already buckled round her wrists and ankles.

Looking for the source of the other noises is easy, he can see she's shut four short straps in the bedroom door, each holding a large chrome steel ring at each corner, turning the door into an improvised bondage frame.

He smiles. This is getting interesting, she's thinking science and bondage.

"Bind me please, Sir" She offers him her wrists.

He grins and pushes her against the door, taking her wrists and secured them to the rings closed in the top of the door. Then he bends down to secure her ankles, holding her spread eagled across the door .

The goggles have been painted over on the inside and padded, to make a blindfold. he chuckles "most creative" as he lowers them over her eyes, plunging her into darkness.

She bites her lip and shudders. He steps back to admire her.

"Now, to unwrap this surprise"

He opens the lab coat and she presses herself back against the door, spreading herself so he got a good view.

She was near naked under the coat, just the white stockings and tiny white bikini bottoms. She's powdered herself near white and across her chest she'd written a complex equation in red pen. he gasps, It's his favourite mathematical derivation!

He growls low in his throat, an almost visceral reaction

"It's like seeing all of Physics naked"

He grins and cups her breast, teasing her nipple between thumb and finger

"Ah ah. Not so fast. I'm your white board. " She rolled her hips. "In the pocket. Take a pen." Her voice was low and husky. "you have to solve for X. "

In the coat pocket are several white board markers

Looking down he realised that on the front of the tiny bikini thong was a big black X.

"Oh, now this is interesting!"

Uncapping a marker he grinned and touched the pen to her breast, flicking it to create a line.

He drew the line longer. Taking his time he covered the upper slope of her chest with small complex symbols. She bit her lip as his pen moved lower, tracing circles round her nipple, the calculation crossing so the double slash equals sign went straight across the other nipple, which was already puckered and hardened.

"Ooops. made a mistake, forgot to carry the 1." Grinning evilly he leaned in and licked her nipple, then roughly rubbed it with his shirt sleeve. She cried out and jerked in the cuffs.

he carries on, down over her flat stomach to the top of her briefs, then started down the outside of her thigh.

When he reached her knee he turned his writing up the inside of her thigh, slowly teasing symbols on her skin. She shuddered, fighting to stay still as he got higher and higher...

just as he reached her panties he switched to the outside of her other thigh, working down with rapid precise strokes. She moaned.

"Almost done, keep still..." his free hand grips her waist, to make her hold still but his thumb is deliberately pressing on the big black x .

She moans and pushed against his hand. His thumb creases the tiny strip of cloth and pushes it into her, making her lips pout around the edges

He reaches her other knee and slowly starts up the inner thigh, drawings closer and closer to the solution...

"And therefore. .. Equal X!" He says triumphantly, drawing the two parallel lines of the equals sign

He strokes the butt of the marker on the white cloth of her panties, already damp with her excitement.

working it back and forth, pushing it in, watching the pink lips of her cunt push round the thin strip of cloth

she moans. "oh, you tease"

he hooks a finger into the cloth and tugs, the knots on the hips pull loose. beneath is a patch of short trimmed hair and her cunt, already swollen and glistening wet with excitement

He teases her open with a finger, One long dextrous finger slips inside, she's hot and wet for him.

With the marker in his other hand he keeps drawing short parallel lines on her mound, each line stroking and teasing

She moans, fighting to keep still and quiet as her hips ride his finger.

He licks at her clit, tongue tracing circles round it as he works a second finger into her, curving them round to stroke inside her

She spasms, pulling hard against the cuffs. "Oh Yes, Yes... I need you... fuck me now, Sir"

He smiles and strokes slowly. "Beg for it."

"please! Please Sir!" She tugs at the cuffs, panting, twisting as he teases her "Please! Fuck me now!"

He unfastens her ankles and lifts her, pressing her against the door, still blindfolded and cuffed

both hands under her ass he lowers her onto his throbbing cock, letting her weight carry her down onto him.

She grips the cuffs and pulls herself up, wrapping her legs around his waist, fighting for leverage to push herself closer to him.

"Yes Sir! oh yes!" he buries himself in her, feeling her desperate need for him turn into a wordless cry as she comes, grasping him tightly. He grunts, his rhythm faster and faster then he grabs her tight as he comes deep inside her, gasping into the shoulder of her lab coat.

...

In the shower the next morning

"Sheldon! These said Non Permanent! "

"That's only for non absorbent surfaces like white boards, not skin"

"WHAT!?"

"Don't worry, solvents will remove them. Perhaps alcohol based hand sanitizer"

"Ouch! ow ow ow That stings!

"Yes, it shouldn't be used on sensitive area. You'll have to let it wear off naturally.

"I'm going to be decorated down there all day?!

Later over chinese take away, Howard asks "Er, Penny, Why do you smell of green apples and gasoline? "

She shrugs "No reason" and scowls at him

Leonard looked surprised. "Erm Penny"

"What now?

"There is a... Well." He cocks his head to one side, puzzled and points at her chest.

Howard leaned forward and leered. "He's trying to There is a lambda drawn in your lovely cleavage."

Penny looks down and shrugs. "So? Math can be sexy"

Sheldon smiles and tucks into his tangerine chicken